The word (or sound effect, depending how you look at it) you say when you're mildly impressed by your girlfriend's appearance, but don't want to get all mushy about it. You know, you cool dudes.
*Sophia comes down the stairs in her new dress*
Michael: (oh, geez, I don't want to be mushy about this. I'm a cool dude. How can I be cool and still give her a compliment? Oh! I know!) "Daaaang!"