not give a rat's arse (about something)

rude To not care in the slightest (about something or someone); to attach no importance to someone or something. Primarily heard in UK. I don't give a rat's arse about making money, I just want to do something with my life that makes life better for others. I haven't given a rat's arse for the show ever since they killed off my favorite character. Do whatever you want, I don't give a rat's arse.