From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( v. t.) To convey, as a message, by means of flag signals; as, to flag an order to troops or vessels at a distance.

(2): ( n.) A flat stone used for paving.

(3): ( n.) Any hard, evenly stratified sandstone, which splits into layers suitable for flagstones.

(4): ( v. t.) To lay with flags of flat stones.

(5): ( v. t.) To signal to with a flag; as, to flag a train.

(6): ( n.) The bushy tail of a dog, as of a setter.

(7): ( n.) A group of elongated wing feathers in certain hawks.

(8): ( v. t.) To furnish or deck out with flags.

(9): ( n.) A group of feathers on the lower part of the legs of certain hawks, owls, etc.

(10): ( n.) A cloth usually bearing a device or devices and used to indicate nationality, party, etc., or to give or ask information; - commonly attached to a staff to be waved by the wind; a standard; a banner; an ensign; the colors; as, the national flag; a military or a naval flag.

(11): ( n.) That which flags or hangs down loosely.

(12): ( v. t.) To enervate; to exhaust the vigor or elasticity of.

(13): ( v. t.) To let droop; to suffer to fall, or let fall, into feebleness; as, to flag the wings.

(14): ( v. i.) To droop; to grow spiritless; to lose vigor; to languish; as, the spirits flag; the streugth flags.

(15): ( v. i.) To hang loose without stiffness; to bend down, as flexible bodies; to be loose, yielding, limp.

(16): ( n.) An aquatic plant, with long, ensiform leaves, belonging to either of the genera Iris and Acorus.

(17): ( v. t.) To decoy (game) by waving a flag, handkerchief, or the like to arouse the animal's curiosity.

(18): ( n.) One of the wing feathers next the body of a bird; - called also flag feather.

Watson's Biblical & Theological Dictionary [2]

אחו , occurs  Genesis 41:2;  Genesis 41:18;  Job 8:11; and סופּ? , weeds,   Exodus 2:3;  Exodus 2:5;  Isaiah 19:6;  John 2:5 . The word achu in the first two instances is translated "meadows," and in the latter, "flag." It probably denotes the sedge, or long grass, which grows in the meadows of the Nile, very grateful to the cattle. It is retained in the Septuagint in Genesis, εν τω αχει; and is used by the son of Sirach, Sir_40:16 , αχι and αχει ; for the copies vary.

"We have no radix," says the learned Chapelow, "for אחו , unless we derive it, as Schultens does, from the Arabic achi, ‘to bind or join together.'" Thus, Parkhurst defines it "a species of plant, sedge, or reed, so called from its fitness for making ropes, or the like, to connect or join things together; as the Latin juncus, a ‘bulrush,' a jungendo, from ‘joining,' for the same reason;" and he supposes that it is the plant, or reed, growing near the Nile, which Hasselquist describes as having numerous narrow leaves, and growing about eleven feet high, of the leaves of which the Egyptians make ropes.

The word סופּ? is called by Eben Ezra, "a reed growing on the borders of the river." Bochart, Fuller, Rivetus, Ludolphus, and Junius and Tremellius, render it by juncus, carex, or alga; and Celsius thinks it the fucus or alga, "sea weed." Dr. Geddes says there is little doubt of its being the sedge called sari, which, as we learn from Theophrastus and Pliny, grows on the marshy banks of the Nile, and rises to the height of almost two cubits. This, indeed, agrees very well with   Exodus 2:3;  Exodus 2:5 , and the thickets of arundinaceous plants, at some small distances from the Red Sea, observed by Dr. Shaw; but the place in Jonah seems to require some submarine plant.

Fausset's Bible Dictionary [3]

 Exodus 2:3. Cuwph Hebrew, the Egyptian Tufi or Sufi . An undesigned coincidence that so many Egyptian words should occur in Exodus, just what we should expect if it be, as it professes, Moses' record; but no Hebrew reared in Palestine long after the Exodus would have had the knowledge of the Egyptian tongue which the many plainly Hebraized Egyptian words in Exodus indicate that its author possessed; nor would the author have used these words with out explanation of their meaning, had he not known that his readers were equally familiar with them. This flag is a species of papyrus, distinct from and less than that commonly used in Egypt to construct light boats, namely, the "Bulrush papyrus (from whence comes our paper), of which Moses' ark was made. (See Bulrush .)

The Cuwph or "secondary papyrus" is again used in the case of Egypt,  Isaiah 19:6. Also "the Red Sea," the sea of suph ( Exodus 10:19). Gesenius explains "seaweed" or "rush"; a seaweed like wool is thrown in quantities on its shores.  Jonah 2:5-6 uses it of "the seaweeds wrapped about his head," for He was not swallowed by the fish at once, but sank to the bottom, where the seaweed was his grave-napkin; thence the fish swallowed him. Another Hebrew word, 'Achu , is translated "flag",  Job 8:11; in  Genesis 41:2 "a meadow." Jerome on  Isaiah 19:7 says the Egyptians told him it meant "everything green growing in marshes"; the sedge, rank reed grass by the river's side. An Egyptian word, Akh-Akh , "green," occurs in a very old papyrus.

Smith's Bible Dictionary [4]

Flag. There are two Hebrew words rendered "flag" in our Bible:

1. A word of Egyptian origin, and denoting "any green and course herbage, such as rushes and reeds, which grows in marshy places."  Genesis 41:2;  Genesis 41:18, (here translated meadow). It is perhaps the Cyperus esculentus .

2. A word which appears to be used in a very wide sense to denote "weeds of any kind."  Exodus 2:3;  Exodus 2:5;  Isaiah 19:6.

King James Dictionary [5]

Flag, L flacceo. See Flaccid. The sense is primarily to bend, or rather to recede, to lag.

1. To hang loose without stiffness to bend down as flexible bodies to be loose and yielding as the flagging sails. 2. To grow spiritless or dejected to droop to grow languid as, the spirits flag. 3. To grow weak to lose vigor as, the strength flags. 4. To become dull or languid.

The pleasures of the town begin to flag.

FLAG, To let fall into feebleness to suffer to drop as, to flag the wings.

FLAG, n. A flat stone, or a pavement of flat stones.

Easton's Bible Dictionary [6]

 Job 8:11 Genesis 41:2,18

In  Exodus 2:3,5 ,  Isaiah 19:6 , it is the rendering of the Hebrew Suph_, a word which occurs frequently in connection with _yam  ; As Yam suph , To denote the "Red Sea" (q.v.) or the sea of weeds (as this word is rendered,   Jonah 2:5 ). It denotes some kind of sedge or reed which grows in marshy places. (See Paper, Reed .)

Hastings' Dictionary of the Bible [7]

FLAG. 1. âchû (  Job 8:11 ), prop. ‘reed-grass’ (cf.   Genesis 41:2;   Genesis 41:18 ). 2. sûph (  Exodus 2:3;   Exodus 2:6 ,   Isaiah 19:6 ), sedgy plants by the Nile and its canals.

Morrish Bible Dictionary [8]

1. achu, a soft reed that can only grow in moist ground: it is eaten by cattle.  Job 8:11 .

2. suph , a weed that grows on the banks of the Nile, among which Moses in the ark was laid.  Exodus 2:3,5;  Isaiah 19:6 .

Holman Bible Dictionary [9]

 Exodus 2:3 2:5 Job 8:11 Isaiah 19:6Plants In The Bible

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [10]

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Kitto's Popular Cyclopedia of Biblial Literature [11]

Fig. 182—Cyperus esculentus

This word (in the original achu) occurs in , where it is said, 'Can the rush grow up without mire? can the flag grow without water?' Achu occurs also twice in;; 'And, behold, there came up out of the river seven well-favored kine and fat-fleshed, and they fed in a meadow:' here it is rendered meadow, and must, therefore, have been considered by our translators as a general, and not a specific term.

From the context of the few passages in which achu occurs, it is evident that it indicates a plant or plants which grew in or in the neighborhood of water, and also that it, or they were suitable as pasturage for cattle. Now it is generally well known that most of the plants which grow in water, as well as many of those which grow in its vicinity, are not well suited as food for cattle; some being very watery, others very coarse in texture, and some possessed of acrid and even poisonous properties. Some species of scirpus, or club-rush, however, serve as food for cattle: S. cespitosus, for instance, is the principal food of cattle and sheep in the highlands of Scotland, from the beginning of March till the end of May. Varieties of S. maritimus, found in different countries, and a few of the numerous kinds of Cyperaceae common in Indian pastures, as Cyperus dubius and hexastachyus, are also eaten by cattle. Therefore, if any specific plant is intended, as seems implied in what goes before, it is perhaps one of the edible species of scirpus or cyperus, perhaps C. esculentus, which, however, has distinct Arabic names: or it may be a true grass; some species of panicum, for instance, which form excellent pasture in warm countries, and several of which grow luxuriantly in the neighborhood of water.

But it is well known to all acquainted with warm countries subject to excessive drought, that the only pasturage to which cattle can resort is a green strip of different grasses, with some sedges, which runs along the banks of rivers or of pieces of water, varying more or less in breadth according to the height of the bank, that is, the distance of water from the surface. Cattle emerging from rivers, which they may often be seen doing in hot countries, as has been well remarked in the Pictorial Bible on , would naturally go to such green herbage as intimated in this passage of Genesis, and which, as indicated in , could not grow without water in a warm dry country and climate.

International Standard Bible Encyclopedia [12]

Two Hebrew words:

(1) סוּף , ṣūph ( Exodus 2:3 ,  Exodus 2:1 , "flags";  Isaiah 19:6 , "flags";  Jonah 2:5 , "weeds"). This is apparently a general name which includes both the fresh-water weeds growing along a river bank and "seaweeds." The Red Sea was known as Yam ṣūph .

(2) אחוּ , 'āḥū ( Genesis 41:2 ,  Genesis 41:18 , the King James Version "meadow," the Revised Version (British and American) "reed-grass";  Job 8:11 , "Can the rush grow up without mire? Can the flag (margin "reed-grass") grow without water?"). Some such general term as "sedges" or "fens" would better meet the requirements.