1. noun, vulgar slang A thoroughly incompetent, foolish, bumbling, or useless person. I can't believe that jack off got elected to the Senate! Get off the road before you kill someone, jack off!

2. verb, vulgar slang To masturbate or bring someone to orgasm, especially a male.

3. verb, vulgar slang To waste or pass time idly or by doing nothing or engaging in foolish behavior. Would you quit jackin' off and help me move this sofa out to the truck?