From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Apple . That the apple ( tappuah ) of the OT is the fruit known by that name to-day is extremely doubtful. It is true that the tree in size and foliage would answer to the reference in   Song of Solomon 8:5 ,   Joel 1:12; the fruit too in its sweetness (  Song of Solomon 2:3 ) and its smell (  Song of Solomon 7:8 ) is very appropriate. It is also suggestive that Heb. tappuah closely resembles the Arabic for ‘apple,’ tuffah . On the other hand, it is a substantial difficulty that the apple does not grow well in Palestine proper, as distinguished from the Lebanon. The native fruit is small and wanting in sweetness; almost all eatable apples are imported from the North. In consequence of this, several fruits which to-day are found in Palestine have been suggested. The citron , a favourite with the Jews on account of its smell and golden colour, is certainly a more recent introduction. The apricot , suggested by Tristiam, which flourishes in parts of Palestine in greater profusion than any other fruit, would seem to answer to the references well. It is deliciously sweet, with a pleasant smell, and, when ripe, of a brilliant golden colour. The tree is one of the most beautiful in the land, and when loaded with its golden fruit might well suggest the expression ‘apples of gold in pictures of silver’ (  Proverbs 25:11 ). Unfortunately there is considerable doubt whether this tree, a native of China, was known in Palestine much before the Christian era. A fourth fruit has been suggested, namely, the quince . This is certainly a native of the land, and is common all over Palestine. The fruit, when ripe, though smelling pleasantly, is not ‘sweet’ according to our ideas, but even to-day is much appreciated. It is a great favourite when cooked, and is extensively used for making a delicious confection. The quince, along with the true apple, was sacred to Aphrodite, the goddess of love.

E. W. G. Masterman.

Wilson's Dictionary of Bible Types [2]

 Deuteronomy 32:10 (a) The apple of the eye is the eyeball. It is very sensitive, is easily injured, and is very valuable to its owner. The expression is used as a type of the nation of Israel, which was, and is, so precious to GOD.

 Psalm 17:8 (a) Here the Psalmist himself takes the place of being the apple of GOD's eye. He felt that he was so easily hurt by his enemies, and yet was so valuable to GOD that he dared to use that type to illustrate his own position before GOD.

 Proverbs 7:2 (a) The Law of GOD is here presented as being just as precious as the apple of the eye, and should therefore be guarded and preserved most carefully.

 Lamentations 2:18 (a) Probably the expression here represents a call from GOD to esteem their position as children of GOD, and the nation of GOD more highly than they were doing. Surely if Israel remembered that they were as the apple of GOD's eye, they would not cease weeping until they were again obeying and worshiping Him.

 Zechariah 2:8 (a) GOD is evidently notifying the world that the nation of Israel is unusually dear and precious to Him, and that He will protect that nation from every enemy. Those who touch Israel in any way to hurt them will in fact put their finger into the eye of GOD.

People's Dictionary of the Bible [3]

Apple Tree, Apple (Heb. Tappûach ). Apple tree is named in the English Versions in  Song of Solomon 2:3;  Song of Solomon 8:5, and  Joel 1:12, The fruit of this tree is alluded to in  Proverbs 25:11 and  Song of Solomon 2:5;  Song of Solomon 7:8. It is difficult to say what tree is intended by the Hebrew word Tappûach . The apple proper is rare in Syria, and its fruit poor. Some writers say the Hebrew word means either the quince or the citron; others speak of the apricot, which is abundant and deliciously perfumed. On the other hand. Dr. Boyle says, "The rich color, fragrant odor and handsome appearance of the citron, whether in flower or in fruit, are particularly suited to the passages of Scripture mentioned above." Neither the quince nor the citron nor the apple appears fully to answer all the scriptural allusions. The orange would answer all the requirements of the scriptural passages, and orange trees are found in Palestine; but it is not certain that this tree was known in the earlier times to the inhabitants of Palestine. The question of identification, therefore, must still be counted unsettled.

Fausset's Bible Dictionary [4]

Hebrew; Tappuach . ( Song of Solomon 2:3;  Song of Solomon 2:5;  Song of Solomon 7:8;  Song of Solomon 8:5;  Proverbs 25:11.) The color was golden, the odor fragrant, the tree green and shady. Probably the citron tree, of which the foliage is perennial, and the blossoms and golden fruit most fragrant. It abounds in W. Asia. In  Song of Solomon 2:5, "Comfort me with apples," the Hebrew is "Straw me," etc., i.e., let my couch be strewed with citrons, to refresh me with their scent, or with citron leaves.  Proverbs 25:11; "A word fitly spoken is like apples of gold in pictures of silver "; i.e., like citrons, antifebrile medicinally, attractive to the eye, pleasing the sense of smell and the palate; served up in elaborately figured silver vessels. Oriental ladies make the citron their vinaigrette.

Webster's Dictionary [5]

(1): (n.) The fleshy pome or fruit of a rosaceous tree (Pyrus malus) cultivated in numberless varieties in the temperate zones.

(2): (n.) Any tree genus Pyrus which has the stalk sunken into the base of the fruit; an apple tree.

(3): (n.) Any fruit or other vegetable production resembling, or supposed to resemble, the apple; as, apple of love, or love apple (a tomato), balsam apple, egg apple, oak apple.

(4): (n.) Anything round like an apple; as, an apple of gold.

(5): (v. i.) To grow like an apple; to bear apples.

Easton's Bible Dictionary [6]

 Joel 1:12 Ishon   Proverbs 7:2 Zechariah 2:8 Psalm 17:8 Deuteronomy 32:10

The so-called "apple of Sodom" some have supposed to be the Solanum sanctum (Heb. hedek), rendered "brier" (q.v.) in  Micah 7:4 , a thorny plant bearing fruit like the potato-apple. This shrub abounds in the Jordan valley. (See Engedi .)

King James Dictionary [7]

AP'PLE, n.

1. The fruit of the apple tree, pyrus malus, from which cider is made. 2. The apple of the eye is the pupil.

Apple of love, or love apple, the tomato, or lycopersicum, a species of Solanum. The stalk is herbaceous, with oval, pinnated leaves, and small yellow flowers. The berry is smooth, soft, of a yellow or reddish color, of the size of a plum. It is used in soups and broths.

AP'PLE, To form like an apple.

Smith's Bible Dictionary [8]

Apple. See Apple Tree .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [9]

Kitto's Popular Cyclopedia of Biblial Literature [10]

The word Tappuach is thus rendered in the Authorized Version. Most authors on Biblical Botany admit that apple is not the correct translation, for that fruit is indifferent in Palestine, being produced of good quality only on Mount Lebanon, and in Damascus. Many contend that 'quince' is the correct translation of Tappuach. Though somewhat more suitable than the apple, we think that neither the quince tree nor fruit is so superior to others as to be selected for notice in the passages of Scripture where tappuach occurs. The citron, we think, has the best claim to be considered the Tappuachof Scripture, as it was esteemed by the ancients, and known to the Hebrews, and conspicuously different, both as a fruit and a tree, from the ordinary vegetation of Syria, and the only one of the orange tribe which was known to the ancients. The orange, lemon, and lime, were introduced to the knowledge of Europeans at a much later period, probably by the Arabs from India. That the citron was well known to the Hebrews we have the assurance in the fact mentioned by Josephus, that at the Feast of Tabernacles king Alexander Jannaeus was pelted with citrons, which the Jews had in their hands; for, as he says, 'the law required that at that feast everyone should have branches of the palm-tree and citron-tree. There is nothing improbable in the Hebrews having made use of boughs of the citron, as it was a native of Media, and well known to the Greeks at a very early period; and indeed on some old coins of Samaria, the citron may be seen, as well as the palm-tree; and it is not an unimportant confirmation that the Jews still continue to make offerings of citrons at the Feast of Tabernacles. Citrons, accordingly, are imported in considerable quantities for this purpose, and are afterwards sold, being more highly esteemed after having been so offered.

The tappuach, or citron-tree, is mentioned chiefly in  Song of Solomon 2:3, 'as the citron tree among the trees of the wood;'  Song of Solomon 2:5, 'Comfort me with citrons, for I am sick of love;'  Song of Solomon 7:8, 'The smell of thy nose like citrons;' so in  Song of Solomon 8:5. Again, in  Proverbs 25:11, 'A word fitly spoken is like apples of gold (or rather golden citrons) in baskets of silver.' In  Joel 1:12, it is enumerated with the vine, the fig-tree, the palm, and pomegranate, as among the most valuable trees of Palestine. The rich color, fragrant odor, and handsome appearance of the tree, whether in flower or in fruit, are particularly suited to all the above passages of Scripture.