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1.
When a guy has no abs whatsoever and is more or less fat in that particular area, he refers to his stomach as a monoceps, similar to stealth abs
John : Dude you should stop eating so much burgers and start working out, your stomach is really getting fat.
Mark : Oh come on youre just jealous of my monoceps.
by pooftwiggy February 24, 2010
 
2.
Slang for the most important muscle in the male body - the penis aka The Monocep.
While many men look to increase their Biceps, Triceps and Quadriceps, I prefer to focus on my Monocep in an effort to truly please the ladies.
by BatmanMuscles July 13, 2013