From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): (v. t.) To form or bend into the shape of an arch.

(2): (n.) Any part of a curved line.

(3): (n.) Usually a curved member made up of separate wedge-shaped solids, with the joints between them disposed in the direction of the radii of the curve; used to support the wall or other weight above an opening. In this sense arches are segmental, round (i. e., semicircular), or pointed.

(4): (n.) A flat arch is a member constructed of stones cut into wedges or other shapes so as to support each other without rising in a curve.

(5): (n.) Any place covered by an arch; an archway; as, to pass into the arch of a bridge.

(6): (n.) Any curvature in the form of an arch; as, the arch of the aorta.

(7): (a.) Chief; eminent; greatest; principal.

(8): (v. t.) To cover with an arch or arches.

(9): (v. i.) To form into an arch; to curve.

(10): (n.) A chief.

(11): (a.) Cunning or sly; sportively mischievous; roguish; as, an arch look, word, lad.

King James Dictionary [2]

'ARCH, n. See Arc.

1. A segment or part of a circle. A concave or hollow structure of stone or brick, supported by its own curve. It may be constructed of wood, and supported by the mechanism of the work. This species of structure is much used in bridges.

A vault is properly a board arch.

2. The space between two piers of a bridge, when arched or any place covered with an arch. 3. Any curvature, in form of an arch. 4. The vault of heaven, or sky.

Triumphal arches are magnificent structures at the entrance of cities, erected to adorn a triumph and perpetuate the memory of the event.

'ARCH, To cover with an arch to form with a curve as to arch a gate.

Hastings' Dictionary of the Bible [3]

ARCH . It is usually stated that the Hebrews were unacquainted with the architectural principle of the arch, but in view of the extreme antiquity of the arch in Babylonian mason work, as e.g. at Nippur, of the discovery of early arches by recent explorers, and of the vaulted roofs of later Jewish tombs, this view is now seen to be erroneous, although the arch is not mentioned in Scripture. The word ‘arch’ does, indeed, occur in the EV [Note: English Version.] of   Ezekiel 40:16 ff., but this is a mistake for ‘porch,’ ‘porches.’ See Temple.

A. R. S. Kennedy.

Holman Bible Dictionary [4]

 Ezekiel 40:16-36 1 Kings 6:3 1 Kings 7:21 1 Kings 7:6  1 Kings 6:2-3 2 Chronicles 3:4 Ezekiel 40:7-26 Ezekiel 40:29-37

Morrish Bible Dictionary [5]

The word elam occurs only in  Ezekiel 40:21-36 , and in the A.V. is translated 'arch;' but this is judged not to be its meaning, though it is not at all certain as to what it really refers. In the margin it reads, 'galleries' or 'porches,' elsewhere 'vestibule,' and again 'projection.'

Easton's Bible Dictionary [6]

 Ezekiel 40:16,21,22,26,29

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [7]

(only in the plur. אֵילִמִּים , Eylammim, masc., and אֵילִמּוֹת , felamoth , fe),an architectural term occurring only in  Ezekiel 40:16;  Ezekiel 40:22;  Ezekiel 40:26;  Ezekiel 40:29, and difficult of definition, but prob. allied with אִיִל , A'Yil, a Ram, hence a column or pilaster ( 1 Kings 6:31;  Ezekiel 41:3, etc.). Most interpreters understand the term (sing. אֵילָם , Eylam') to be the same as ץוּלָם , Ulam', a vestibule or Porch, following the Sept., Vulg., and Targums ( Αἰλάμ , Vestibulum, ץוּלִמָּא ) ; but it is manifestly distinguished from this

( Ezekiel 40:7-9;  Ezekiel 40:39-40), since the latter contained windows ( Ezekiel 40:16;  Ezekiel 40:29), whereas this was carried round the building, even in front of the ascent to the gate ( Ezekiel 40:22;  Ezekiel 40:26), and is usually associated with pillars. Of the other ancient interpreters Symmachus and the Syr. translate sometimes surrounding coliumns, sometimes threshold. The word appears either to denote a portico with a colonnade, or (according to Rabbi Menahen) is about equivalent to אִיִל , from which it is derived, i.e. some ornament, perhaps the Volute or moulding at the top of a column (comp. Bottcher, Proben Alttest. Schrifverkl. p. 319).

Arches with vaulted chambers and domed temples figure so conspicuously in modern Oriental architecture, that, if the arch did not exist among the ancient Jews, their towns and houses could not possibly have offered even a faint resemblance to those which now exist; and this being the case, a great part of the analogical illustrations of Scripture which modern travelers and Biblical illustrators have obtained from this source must needs fall to the ground. Nothing against its existence is to be inferred from the fact that no word properly signifying an arch can be found in the Hebrew Scriptures (see above). The architectural notices in the Bible are necessarily few and general; and we have at this day histories and other books, larger than the sacred volume, in which no such word as "arch" occurs. There is certainly no absolute proof that the Israelites employed arches in their buildings; but if it can be shown that arches existed in neighboring countries at a very early period, we may safely infer that so useful an invention could not have been unknown in Palestine.

International Standard Bible Encyclopedia [8]

arch ( איל , 'ayil  ; Septuagint τα αἰλάμ , ta ailám , in sense of "posts" or "colonnade"): Referred to repeatedly in  Ezekiel 40:16 , but translation is an error for "porch" or "portico." the Revised Version (British and American) gives in marg, "or, colonnade . The meaning of the Hebrew word is uncertain." The principle of arch construction was known to the Jews and examples of early Jewish rude arches have been found in Palestine. An arched form need not necessarily be constructed with radiating joints; it can be corbelled as at Mycenae (Treasury of Atreus). This type of construction has been found also in Palestine.