Definition from Wiktionary, the free dictionary
cootie (plural cooties)
- (rare) A nest-building female American Coot (counterpart to Cooter).
- (North America, colloquial) A louse.
- (North America, colloquial, childish, usually plural) Any germ or contaminant, real or imagined, especially from the opposite gender (for pre-pubescent children).
- I’m not drinking from his glass until I wash the cooties off it.
louse — see louse
slang: germs or contaminants