A snarky, obstinate person who appears to be definiant for no good reason, although they likely have one and aren't telling you. They are masters of walking the line between displaying affection and acting like they don't care.
Watch out for emoticons like this
:^)
I would have married him, but he was a tough cookie.
When you crush some cookies, stuff them in her vagina and ass then eat her out and all remnants of cookie are rubbed in between her titties until she likes it
Person 1: Damn dude I ran out of Oreos for my Cookie Monster surprise so I had to use chips ahoy
Person 2: Damn that sucks, we know the best Cookie Monster surprise is with Oreos