A guy who, rather than risk rejection by asking women out, forges friendships with them hoping that eventually it'll lead to romance. A Nice Guy will often claim that they treat women with respect and then get angry when they don't reward him with sex.
Not to be confused with a guy who is geuinely nice.
Nice Guy: All these other guys treat girls like shit! I've never gone around acting like an asshole! Why don't you date me? It's not fair!
Woman: I'm sorry, am I supposed to be interested in you just because you meet minimum standards of decency?