1. The action a guy is doing when masturbates.
2. A person who is a motherfucking asshole dipshit. Basically. Also can be called a Jerkoff. (See 'Jerkoff' for more information.)
3. A nickname you give to someone named "Jack".
1. I had some good porn in front of me, so I just had to jackoff to it.
2. Guy: *Slaps girls ass*
Girl: Damnit! You're such a Jackoff!
3. For Jack's birthday, I gave him a card that said "To Jackoff"