noun
A polite term for a public toilet, often used in department stores, hotels, and similar facilities.
デパートのレストルームはとても清潔だった。
The restroom in the department store was very clean.
noun
resting room (with toilet facilities)
A room for resting that usually includes toilet facilities; less common than the simple 'toilet' sense.
空港のレストルームで少し休んだ。
I rested for a while in the airport's resting room.