From Longman Dictionary of Contemporary Englishpowder your nosepowder your noseDCBan expression meaning to go to the toilet, used by women to avoid saying this directly She’s just gone to powder her nose. → powder
Examples from the Corpus
powder your nose• You get the drinks in - I'll just go and powder my nose.• After the main course Vanessa disappeared to powder her nose.• One way or another, I had drunk quite a bit this evening, but I didn't need to powder my nose. 