When a person leans their back against a wall, usually outside, and defecates.

(noun) A successful type of theft which results in an acceptable, impressive and rewarding payday for the protagonist.

A longish extrusion of fecal material stuck to the skin of the left or right ass-cheek, that is free enough to lean to the right or left, front or back, depending on the angle of the bum relative to the toilet seat. May or may not be fully extruded from the balloon knot, but must be attached to the cheek in question. May be partially submerged in the toilet water, if long enough. Requires a vigorous shaking of the butt cheeks and possible sphincter contraction to dislodge, followed by extensive butt-wiping to ensure proper hygiene.

when a guy is taking a pee and has to use the wall to hold himself up from the great feeling

A leaner is a person that uses the betterTTV Leanin emote in twitch chat.
Leaners usually occur in large groups and therefore bother moderators of the twitch.tv channels such as Thebausffs.
In early stages moderators timed out Leaners, which angered others and therefore also drove them in the hands of the cult of the Leaners. Since banning people fulfils moderators omnipotence fantasies they try to achieve a Leanin-equilibrium by banning enough Leaners for the cult to not die out, but not too much so that the chat would completely get run over by the Leaners.

A person who leans over the table while shooting in a game of beerpong.

A line of coke.

You know, you gotta lean over to get at it.