Boyd’s Bible Dictionary:
(serpent). An animal of the lizard species. Evidently a wild beast, as a jackal (Job 30:29; Isa. 34:13; Psa. 44:19; Jer. 9:11; Mic. 1:8); sea-serpent (Gen. 1:21); land-serpent (Ex. 7:9-12; Deut. 32:33); devil (Rev. 12:3-17).
Concise Bible Dictionary:
It may signify any great serpent or sea monster, symbolical of a huge destructive creature. Nations doomed to destruction and desolation, including Jerusalem, are said to become habitations of dragons (Isa. 34:13; Isa. 35:7; Jer. 9:11; Jer. 10:22; Jer. 51:37). Pharaoh, king of Egypt, is called the great dragon (Ezek. 29:3). As one of God’s creatures the dragon is called upon to praise Jehovah (Psa. 148:7). In the New Testament the dragon is a type of Satan and those energized by him. In Revelation 12:3 the “great red dragon, having seven heads and ten horns,” is symbolical of Satan’s power in the form of the Roman empire: it endeavored, in the person of Herod, to destroy Christ when born. In Revelation 13:2, 4 it is Satan who gives the resuscitated Roman empire in a future day its throne and great authority. In Revelation 13:11 The Antichrist, who has two horns like a lamb, speaks as a dragon. In Revelation 16:13 it is Satan, and in Revelation 20:2 he is described as “that old serpent, which is the Devil and Satan.”