Indifference towards people, things, and/or activities. Lack of emotion and lack of feeling, numbness.

I don't really care.

Indifference towards the world; jaded personality; numb, uncaring attitude; could be described as what an emo person feels and acts like.

When you don't have emotion or don't show emotion. Indifferent, uncaring.

(A)pathetic individual who lacks the will power/motivation to care enough about anything. Usually very whiny and pessimistic, often suffers from existential depression. One who is apathetic often possesses at least a small portion of an angster's qualities, but eventually dismisses them after they are deemed unimportant like everything else.

Someone who really doesn't give a darn.

Means something, dunno what though, and to be fair who cares? I don't.