Dragon in Wikipedia
Dragon, a word frequently found in the translations of the Bible as substitute, so it seems, for other names of animals that the translators were unable to identify. It stands indeed for several Hebrew names:
(1) thán (Job 30:29; Isaiah 34:13; 35:7; 43:20; Jeremiah 9:11; 10:22; 14:6; 49:33; 51:37; Micah 1:8; Malachi 1:3), unquestionably meaning a denizen of desolate places, and generally identified with the jackal;
(2) tánnîm, in a few passages with the sense of serpent [Deut., xxxii, 33; Ps., xc (Hebr., xci), 13; Dan., xiv, 22-27), in others most likely signifying the crocodile [Ps., lxxiii (Hebr., lxxiv), 13; Is., li, 9; Ezech., xxix, 3], or even a sea-monster (Ezekiel 32:2), such as a whale, porpoise, or dugong, as rightly translated Lam., iv, 3, and as probably intended Ps., cxlviii, 7;
(3) líweyãthãn (leviathan), meaning both the crocodile [Ps., lxxiii (Hebr., lxxiv), 14] and sea-monster [Ps. ciii (Hebr., civ), 26];
(4) çiyyim (Psalm 73:14; Jeremiah 1:39), which possibly means the hyena.
Other places, such as Esth., x, 7; xi, 6; Ecclus., xxv, 23, can be neither traced back to a Hebrew original, nor identified with sufficient probability. The author of the Apocalypse repeatedly makes mention of the dragon, by which he means "the old serpent, who is called the Devil and Satan, who seduceth the whole world" (Revelation 12:9, etc.). Of the fabulous dragon fancied by the ancients, represented as a monstrous winged serpent, with a crested head and enormous claws, and regarded as very powerful and ferocious, no mention whatever is to be found in the Bible. The word dragon, consequently, should really be removed from Bibles, except perhaps Is., xiv, 29 and xxx, 6, where the draco fimbriatus is possibly spoken of. See BASILISK, 4 (sup.).