1. Verb - to press up against or to jostle.
2. Noun - the end part of a rifle or shotgun or machinegun that rests against the shoulder or pectoral muscles to increase stability during firing.
3. Noun - the part of a human being that knows wind and earth. The buttocks and anus of a person.
4. Noun - the recipient or target of a joke.
Two of the round cheeks below your back and above you thigh. Used to do things like fart and jiggle. There are other terms like booty, behind, cheeks, etc.