A Boy (is a boy no matter what age, shyguy/shyman is an oxymoron) who doesn't beleive in himself and exhibits this with fear of interacting with other people. If he does have a girlfriend, she is usually a fat girl. Contrary to popular belief, shy girls go for macho men, not their apparent shyguy counterpart, unless of course the shy guy is tall and handsome, then he can luck out and get shy nerdy girl.
Wow, Robert is such a shyguy.. Look at him walking down the street with his head hung down. I wonder how come he never looks me in the eye when talking to me?! Ah, but that fat girl walking with him don't care, because she knows its the best she can do!