jerk muscle

The muscle developed in the forearm from jerking off too much. Often exaggerated amongst friends to make one appear to jerk off more than they might.

Mike: Dude, you been going to the gym yet?
Nate: I started going a week ago.
Shannon: Don't listen to him, we broke up a week ago and that's just his jerk muscle gone crazy.

by Skrait Buttah July 29, 2006

jerk-off muscle

a muscle built and strengthened by everyday masturbation, a.k.a brachioradialis

Dorothy: Whoa, look at your arm muscle! You've been working out, huh?

Bob: ummm... it's my jerk-off muscle...

by Joedaman March 19, 2010