When a man thrusts his cock back and forth between the forearm and a huge flexed bicep of a very muscular woman or man.
Vince was having the best muscle sex ever with his immensely muscular girlfriend, Lin.

She whispers into his ear, "I'd love for you to give these bulging biceps a nice cepjob with that throbbing cock of yours."
by Rinji January 31, 2011
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