ladies' noun3 •possessive case of lady: belonging to some or all ladies. •(informal, euphemistic) Ellipsis of ladies' room (“a lavatory intended for use by women”).Kemp left me to go to the ladies'. I pulled out a paperback I had in my pocket. — 1968 •(informal) Ellipsis of ladies' department: a section of a department store where clothing is sold for adult females.