Jack Dempsey 

A "Jack Dempsey" refers to one beating his meat very aggressively, as the legendary boxer Jack Dempsey flogged his opponents.

Dude, I got so excited over that midget porn I was watching that I stole some face cream from my sister's make-up bag and gave myself a "Jack Dempsey". Now my pecker is sore.

Jack Dempsey by Midnight Stroker August 21, 2008

Jack Dempsey 

A man who owes the majority of his fame to a fish.

I didn't know who Jack Dempsey was until I went to the "aggressive cichlids" shelf in petco

Jack Dempsey by Necrozma Beam January 11, 2021