We say or use this phrase when we don't care or are not interested in what someone says or does.

One who has a mania for music.

An ailment that causes one to not care about the consequences of their actions or give up on their goals.

I don't give a shit is a popular phrase to be used when you are not interested in what someone else says or believes. It implies that you don't even care enough to physically give them a sample of your fecal matter.

When you just dont care, could also be paired with I dont give a fuck

The act of not caring about something.

The most polite and courtesy way of telling someone to leave you alone.