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1.
A bump of muscle usually close to the elbow that is said to indicate if someone frequently masturbates.
Did you see Dave's beater's bump. . .that guy must whack off a lot!
by Rafael Lewis April 16, 2006
 
2.
A lump of muscle on the arm, near the elbow that is said to indicate if someone frequently masturbates.
Some people joked that Carl whacked off a lot because he had a giant beater's bump on his arm.
by Rafael Lewis April 05, 2006