gentlemen's

noun2

1. •
   possessive case of gentlemen: belonging to some or all gentlemen.
2. •
   (informal, euphemistic) Ellipsis of men's room: a lavatory intended for use by men.

   • Over on that platform's the general waiting-room,... and over there's the Gentlemen's, and, any'ow, everythink's written up. — 1933