used to emphasize rudely that you do not think something is important

"It looks as if we are going to lose." "Who cares?". “看来我们好像要输了。”“谁在乎呢？”

"I don't suppose she'll want to work with us again." "Oh well. Who cares?"

"I don't think Peter's going to be happy when he hears about this." "Who cares what Peter thinks?"

"I guess they won't be visiting us again." "Probably not, but really - who cares?"

I probably should have worn something a little smarter for the occasion. Ah, who cares? What matters is that I'm here.

See also: care verb (WORRY)