Hammer arm

When a male masturbates with one arm more than the other causing it to be muscularly bigger than the other one.

Guy 1: "Yo whys your one arm so big son?"
Guy 2: "Ahh i got Hammer arm, i jackoff with my dominate arm more then the other one so it's just uneven."

Guy 2: "Sounds like you needa switch it up a bit man."