A wet ho, take on H20 (water), signifying constant vaginal lubrication due to constantly sexing everything that moves.

This is a modern urban American take on the British "watery tart," of Monty Python fame, named for the same characteristic.
Snobby Englishman: My sister is so the watery tart, wot?
Urban Speaker: Yo, she a regular H to thuh O.
by Col. Dr. April 24, 2006
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