A male who is friends with a female. This is used in contrast boyfriend. A guyfriend is just a friend who happens to be a guy; a boyfriend is someone you are dating.
see also galfriend.
Lindsay: "So, are you dating Chad?"
Mary: "No, he's just my guyfriend."
a dude, a fun guy to hang out with and talk to when all ur girlfriends are bein goofballs. u usually end up dating ur guyfriend for a while but it hardly ever works out cuz hes basically ur brother
girl: ur my best guyfriend
boy: i know, but i kinda want to be your boyfriend
girl: o well i guess we could try that
Noun: An individual that will befriend your woman, against HER better judgement, only to try to get in her pants through the use of building bonds/pity/lies/sneaking around because they know that if you knew that she was friends with HIM you would assault HIM.
Guyfriends are not trust worthy and normally carry diseases such as herpes and HPV. These will STD's will generally go unnoticed until YOU contract them, then SHE will blame you to hide her guilt.
DUDE: "I don't like him, he has cheated on his woman before. But now I'm suppossed to just trust him with you?"
DUDE: "I don't. He's a liar and he has openly told other people he wants to bang you."
CHICK:"He didn't mean it, he's my pal, my GUYFRIEND. And he means more to me than any of my other friends, he doesn't judge me and he is there when you and I are arguing to keep me sane and tell me I am being dramatic. He has kept us together more than once."
DUDE: "Pack your crap if you can't NOT be his friend, because I'm not gonna stand for it."
CHICK: "Fine, I'm leaving." -she leaves