Top Definition
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."
by killerseemroe January 06, 2012
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