Usually a confirmation of a statement or an utter agreement with a person's self.
Man, you fuckin' gay!
a way of agreeing with something
-Ha! You so crazy!
synonyms: word up, right on, amen, agreed upon.
Let's say someone, in a crowded place, shouts, "war sucks!" Damn straight would be an appropriate reponse to that exclamation if you are anti-war.
Person 1: Wow, this band is awesome!
Person 2: Damn straight!
An affirmation, usually to a preceeding statement.
'Id rather be done up the butt than see that guy again' .. 'Damn Straight!'
As has been mentioned, a way of agreeing with something, but I always found it to be almost condescending (in a cool way.) It seems like a "grown-up" way of saying "duh" almost.
John McCain: I'm a conservative but even I think our former president was a bit of a fuck up.
Talking giraffe: Damn straight.
Something Jayne Cobb from the popular TV show Firefly would say if someone told him how awesome his hat was.
Kaylee: I think it's the sweetest thing ever.
Wash: A man walks down the street in that hat, people know he's not afraid of anything.
Jayne: Damn straight.