When a girl is giving a guy a really good blow job, and after a few minutes into it she stops and punches him as hard as she can in the balls.
Or...
Tell a guy you want to give him a blow job, after he pulls down his pants wait a few seconds and give him a SUPER punch to the balls.
A small annoying dog, often of the chiwawa breed or similar. Essentially suming up the regular definition in Dog form as in something a wife or girlfriend would buy to metaphorically punch the husband/boyfriend in the balls on a daily basis.
Tom: I got laid last night with Julie
Bill: OMG HOW SHES SOOOOOO OUT OF YOUR LEAGUE
Tom:I don't know either. It was so good though when i started fuck punching her
Brad: hey Riki, did you bone that chick Carol from the bar last night?
Riki: I sure did bro, unfortunately for me though I couldn't feel a thing, she had a fanny like an empty punching bag.