*Ahem.* This is the place of convenience. What place above all others do you want to be convenient? Just in case, you know... that would be the toilet. You might also call it the lavatory, the restroom, or the bathroom.

This word is casual and sounds gruff, so you won't see it on offical signs or hear it in polite conversation. It's worth knowing so that you'll understand it in casual speaking and writing, though.