powder your nose (of a woman) go to the lavatory.
☞ This is an early 20th-century euphemism, which is now rather dated. The term powder room has been used since the 1940s to refer to a ladies' toilet in a hotel, restaurant, or similar public building.
1972L. P. DaviesWhat Did I Do Tomorrow? I'll use your bathroom. To powder my nose, as nice girls say.