sexually insecure 

A guy who feels doubt about his manliness or what other people perceive of him as a man, and tries to make up for it by getting attention for obnoxiously doing "manly" things like drinking a lot, constantly revving a car or motorcycle and going at high speed unnecessarily, playing very loud "manly music" like heavy metal or hip hop, and reacting wildly at the slightest provocation, usually by threatening or attempting to physically harm whoever provoked him. The reaction will be stronger if the provocation suggests that he might not be "man enough", like being a pansy, a homosexual, unable to get women or having a small dick. He may even refuse to do chores traditionally assigned to women like cooking, babysitting or doing the laundry, because he feels doing such chores would cast doubt on his manhood. Usually shortened to insecure depending on the context.

The South Park episodes "The New Terrance and Phillip Movie Trailer" and "The F Word" have highlighted some behavioral traits of such sexually insecure people.

sexually insecure by MiniChimera January 16, 2011