louse

(noun) wingless usually flattened bloodsucking insect parasitic on warm-blooded animals. Synonyms: sucking louse.

(noun) a person who has a nasty or unethical character undeserving of respect. Synonyms: worm, insect, dirt ball.

(noun) any of several small insects especially aphids that feed by sucking the juices from plants. Synonyms: plant louse.

(noun) wingless insect with mouth parts adapted for biting; mostly parasitic on birds. Synonyms: bird louse, biting louse.