1) Your opinion of a certain thing; be it a movie or a new car
2) Refusal to accept minor gifts
3) Waving off a thank you from peers
4) Telling others to leave it all to you
It's cool bro, I got them
This can be quite confusing at first because this really means the opposite of cool. When you hear this term, its really not cool in fact it couldn't be more un-cool. Often hearing this means that the person thinks what you just said is totally un-cool, gay and that they are very upset, the person may in fact want to now punch a baby.
Me: Hey can I call you right back, Mike was trying to grill and there is a flaming whore running around in our backyard now. I really need to put her out.
Adeline: It's cool, call me whenever.