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.

Someone who is possessed by clout chasing. The original human is now gone and a demonic entity that feeds on clout is all that is left. An empty shell with no control of their actions, forced to blindly react to situations they think will bring them attention.

A man who admires other mens rear ends, with thoughts of buggering the admired rear end.

While performing intercourse doggystyle, the man pulls the womans hands behind her back and attempts to thrust her around a room. A full circuit around the room will make you a rear admiral.

A senior rank in the Navy.

This term refers to a person who likes to stick long phallic-like objects up their rectum. The term was coined in the 1970s to describe high-ranking military officials who enjoyed poking their intestinal basin with objects that are similar in shape to a man's genitals. The motivation for this is unknown and the term is usually used in a derogatory fashion to describe someone.

The act of engaging in intercourse with a woman from behind and using the momentum of your movement to propel you across a room. A performer of the rear admiral must hold his hands in the air so as to not balance or steady himself.