A dumb question or response. Something one shouldn't even have to think about it.
Dude1: Hey, man, where's the basement?
Dude2: Try downstairs, bright spark!
Girl: Whales are... big.
Something so obvious to be correct/appropriate, that it requires no contemplation to decide on.
It was a no-brainer for Zack to wear a condom when he banged that disease infected whore (ewwwww).
could be used as in "definetly" or "of course"
Jim: Do you have to put your marshmallow in the fire?
Clark: Dude, it's a no brainer, as a rule of thumb campers should put their marshmallow in the fire.
Not needing a brain to operate task in question
Hey, working a till in Macdonalds is a no brainer which is just as well as chavs need the work
A question with an obvious response.
Dude 1: Will you take the money?
Dude 2: Yes I will! It's a no brainer.
noun. A person (particularly a female) who will gladly accept head but wont return the favor. Most commonly technical virgins who aren't yet accustomed to much sexual behavior. (Or simply just a prissy bitch)
Kenny: Hey you know any females that give good head?
Eli: Ohhh! how bout Jessica? Dude, I heard that girl swallows!!!
Kenny: wtf? Oh hell naw man she's definetely a no brainer. and her dad's a cop..you got me fucked up dawg.
A person of either the male or female persuasion who absolutely refuses to participate in oral sex.
'Man, I had to leave that girl alone. The p***y was good, but I found out she's a no brainer-she wouldn't give me any head!"