A sexual act, performed to humiliate another, usually a woman. The man shaves his pubic hair, leaving it until he ejaculates in the females face, then throws the hair into her face where it sticks and shouts "monkeyface!". Alternatively the man may decide to rip his or his partner's pubic hair out at the moment of passion and throw it into the mixer.
"Upon sighting the White Whale, Captain Ahab grabbed Queeqeg and forced him roughly to his knees where he gave him a monkeyfacing, in the New England style". From Moby Dick by Herman Melville.