Wiktionary
good guy
n. 1 (context informal English) a hero 2 (context informal English) an all-around pleasant person; usually used in reference to a male.
WordNet
good guy
n. any person who is on your side [ant: bad guy]
Usage examples of "good guy".
They fought to three pins, and when it was over, shook hands and headed back for the barracks, Romlar telling himself that Carrmak was a good guy.