Sex. Created by a small group of kids, but I saw some guy say it on a forum, so I figure it's time to represent. Extra boinks can be added for effect as in "sheboinka-boinka."
Noun: I heard that kid was doin' the sheboinka with some skank-ass bitch.
Verb: I want to sheboink your mom.
A younger male who, although not taking any medication to do so (hormones, Premarin), appears head-to-toefully feminine when dressed like a genetic female.
Mallory is the hottest sheboi I've ever seen! You've got to see her videos!