Oak is used as a slang word for 'Okay'. It is usually a word that you use to someone that you don't care about, or used even if 'okay' isn't the right word torespond with.
A boy you can trust, never leaves your side and always has your back! He will make you feel so special, comfort you, open to you and make you laugh! He can make you laugh instead of cry smile instead of frown and have faith when there seems like none! He’s somone you’ll never forget and if your lucky enough to have him hold on to him. He’s also a sexy beast!!
Guy 1: Can you get my glasso' water over there?
Guy 2: Oak
Guy 1: Oak? Are you fuckin' retarded?
Guy 2: Oak
Guy 1: Uh...
Guy 2: O A K.
Guy 1: Ok...
Guy 2: There ya go
Guy 1: ????