gents'

possessive case of gents: belonging to some or all gents.

A gents' toilet room might be found in a house that caters for the cheaper class of theatrical patronage, where the slangy language of the "goin' to the mat this aft?" style prevails. A gents toilet room is not found in the Southern Hotel. It either "men's" or "gentlemen's".

...our modern man in Hong Kong excuses himself to go to the gents'. The broad window overlooking the lights of Hong Kong in the gents' loo is astonishingly elevated too, and as he relieves himself, gazing out into the night of diamond dust, across the fairy glimmering of the city, he feels something shift in a subtle way...

Synonym of men's room: a lavatory intended for use by men.

"I'm dressed as a woman, but I am still technically a man. I believe that to comply with the law of the land I ought to continue to use the Gents', but in order not to look out place I intend to use the Ladies' from now on. I trust none of you will grass on me..."

I asked the way to the restroom. A young lady pointed the way and said, "I'm afraid you'll have to use the Gents', they're painting the Women's."