From an interview with "The Simpsons" creators.
Regarding "Rear Admiral," I think the answer is probably as disappointing as you feared it might be: it doesn't exist. Here is the actual first draft script excerpt from the Halloween show:
BART: Milhouse. Milhouse, wake up. Quick, look out the window.
MILHOUSE: No way, Bart. If I lean over and put my face against the window, you're gonna smash it, or maybe pinch my butt real hard.
This was the first draft. In re-writing it, the writers wanted to go for something a little funnier, something that would sound like it was from the family of "flying wedgie," "purple nurple," etc. Someone, I do not remember who, said "Rear Admiral." It sounds real, having the word "rear" in it, but it was manufactured to sound real. As far as we know, it doesn't really exist.
Bart: Milhouse...Milhouse, wake up, quick! Look out the window.
Milhouse: No way, Bart. If I lean over, I leave myself open to wedgies, wet willies, or even the dreaded rear admiral!
Where a couple starts having sex in the classic doggy position; then when he is ready to spit seed, he dismounts, leaps onto the woman's head and shoots for distance as she rears up.
Last night I performed the Rearing Unicorn on my wife.
someone's part of body they sit on; butt.
Look at that girls big rear end.
to stick one's testicles in a girl's anus.
see dog in a bathtub
"...her ass is pretty loose so I decide to pull the rear bagger and she's cool with it..."
eager to begin; sometimes "raring" to go; the metaphor is equestrian and like other equestrian allusions "champing at the bit" it connotes that something or someone else is in control, in this case preventing immediate gratification
The twins were rearing to go on the drive to Disney World.
To be one of two other people out with a couple in a typical couple situation. A third wheel plus one.
"Want to help me rear axle Kenny and his bae tonight?"
"Ugh, I don't know if I'm into that sort of thing."
"Nah man, I just mean hang out with the three of us."