serpent

1. (now literary) A snake, especially a large or dangerous one.Examples: "He falls into it, who has digg'd a Pit. Who breaks a Hedge is with a Serpent bit."; "Coiled up behind the shrub, […] was a green imamba, the most dreaded of all South African serpents."; "Any serpent six feet long looks formidable; and over that length, one takes on the aspect of a chimera."literary

2. (figurative) A subtle, treacherous, malicious person.Examples: "He is a very serpent in my way."; "'Dogs and serpents,' She began in a low voice that gradually gathered power as she went on, till the place rang with it. Eaters of human flesh, two things have ye done. First, ye have attacked these strangers, being white men, and would have slain their servant, and for that alone death is your reward.'"figuratively

3. (music) An obsolete wind instrument in the brass family, whose shape is suggestive of a snake (Wikipedia article).

4. (mythology, fantasy) A snake-like monster, such as a dragon or sea serpent.Examples: "Then Beowulf too rallied. With his whetted dagger he slit a gash in the serpent's middle."