1A person who studies or collects insects or other bugs; an entomologist. Often somewhat depreciative.

2A substance or device used to deter, control, or kill insects and other bugs; an insect repellent; an insecticide.

3North American informal (usually depreciative). A person who studies or investigates bacteria, viruses, etc., or the diseases caused by them; a microbiologist or epidemiologist.

4Slang. A person (especially a homosexual man) who actively seeks infection with the HIV virus through unprotected sex with HIV-positive partners.