As said by the previous poster: shorter, cooler version of whatever.
Used when people pretend they don't care enough about what they're saying to add the extra syllable. Or, they're not really serious about the negative connotations that go along with "WHATEVER."
Also see whatevs
Ah I look bad today, but whatev.
Person 1: You forgot to dot your i's!
Person 2: Hehe, whatev!