A friend girl is a girl you really like, but you're just really close friends and not boyfriend/girlfriend. You're still in the friend zone and that's ok.

A casual invitation / threat used by an individual that is not afraid of fucking someone up.

A female you don't want to screw. She could be unappealing, not interested, her bothers would rip you dick off. Or very rarely you value this person so much you would rather keep her as a friend , then risk loosing her as a lover.

A woman with whom you are friendly but not in any way romantically linked.

A girl who is just a friend. In other words a girl who is a friend. They do not engage in sexual activities of any kind, but at the most there might be hugging or holding hands. Many guys whine that they want to be her girlfriend instead of a friend.
One sided sexual attraction is possible on the girl's part as well. However girls and guys should realize that doing stuff like asking their friend out is annoying to say the least and should be avoided. It's perfectly normal to have a friendgirl and you don't have to have sex with someone just because you're close to them and they are the opposite sex.

Essentially the same thing as a girlfriend, only the two are actually just friends. Basically a female best friend that a guy also hangs out with, like when his girlfriend's busy. It's not a sexual thing.

A girl who is your friend, who you would like to be your girlfriend, but who will almost certainly never BE your girlfriend.