(one) can't be arsed

rude slang One is unwilling or disinclined to make the effort necessary (to do or accomplish something). Primarily heard in UK. I couldn't be arsed to clean all those dishes after dinner, so I just left them in the sink until the morning. Apparently, my kids can't be arsed to put their clothes into the linen basket like they're supposed to. Graduation is right around the corner, so I can't be arsed to study for tests anymore.

can’t be ˈarsed (to do something)

(British English, taboo, slang) not want to do something because it is too much trouble: I was supposed to do some work this weekend but I couldn’t be arsed.

A more polite way to express this is ‘can’t be bothered (to do something)’.