(n) A male who, by age, should be a man, but still acts childish, is oblivious of what acting grown-up is about. An insult to point out ridiculous immaturity. A pathetic example of taking responsibility or manhood.
Man-boy clues: You are over 25, not in school and...
still live with parents (excluding illness or tragedy), still twist your friends nipples on a daily basis, buy toys off ebay for yourself, think "picking up chicks" is all in strategy of a well-delivered pick-up line, use status or lie about what you do to impress women, have a child and are still out partying like you are in high school while trying to pick up much younger girls.
That freakin' man boy tried to play off his 'rents as roommates and then he show me his KISS collection. What is he - 32 now?