louse

noun

1. 1

   wingless usually flattened bloodsucking insect parasitic on warm-blooded animals

2. 2

   wingless insect with mouth parts adapted for biting; mostly parasitic on birds

3. 3

   any of several small insects especially aphids that feed by sucking the juices from plants

4. 4

   a person who has a nasty or unethical character undeserving of respect