When someone with huge upper-arms flexes, and their bicep then proceeds to hit youin the face. See: punch.
Similar to: kneed, elbowed, and head butted.
Lindsey: Tom! Your muscles are so big, flex them for me!!
*flexes*
Lindsey: OW, you totally just bicepped me in the face! Thanks for showing me that they were real!
A person with rather abnormally large biceps , the beast refers to the sheer power the biceps have, this person would normally have massive triceps and a large penis.
This rare breed of people are referd to as, Scott or Batman