ALT 1: To have sex that you can pretend isn't sex, typically because it doesn't involve vaginal penetration. Requires delusional level of religious belief involving purity vows, etc.
ALT 2: To masturbate
Sexual euphemism reflecting media clusterfuck
around Christine O'Donnell, bizarre non-sex lobbyist who is/was the teabagger
2010 Republican US Senate candidate in Delaware.
Dan Savage, Savage Love | Letter of the Day | 9/20/10:
Considering 1. his presence every time you're messing around with her (surely the library, the living room, or your room would've occurred to him if he were uncomfortable being in the same room while you fingered / O'DONNELLED his girlfriend) and 2. the limitations she's placed on the sex she's willing to have with you, and 3. his tendency to suddenly "show interest" after you've been messing around with his girlfriend (at which point you "move over" and, presumably, out), I'm thinking your girlfriend's primary partner has a bit of cuckolding lite/sperm competition syndrome thing going.