wen engaging in sexual activity, just before the male ejaculates he yells tuna surprise, at which point a friend jumps out the wardrobe and slaps the female in the face with a fish

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

While performing oral sex on a woman, the giving parter spreads the labia and screams "SURPRISE!" into her vagina

When a pervert or deviant abuses a large-mouthed fish for sexual gratification, filling it with a substance resembling mornay sauce. An act of grievous fish-abuse.

a fishy ass pussy