Loo
What it really means
The toilet. A polite, everyday British word — you can safely use it anywhere. "Where's the loo?" is the natural way to ask in someone's home or a pub.
Context, tips & common mistakes
Loo is the all-purpose polite-informal word for the toilet, safe from pub to dinner party: 'where's the loo?' embarrasses nobody. 'Toilet' is equally fine and universal. The words to unlearn are the American ones — 'bathroom' in a British house means the room with the bath, and 'restroom' draws blank looks; 'Gents' and 'Ladies' label public facilities, and 'lavatory' or 'WC' survive mainly on signs.
The practical layer: free public toilets are scarcer than newcomers expect, so the working knowledge is which places let you go — department stores, supermarkets, pubs and cafés (as a customer), museums and libraries. Asking staff 'sorry, could I use your loo?' with a purchase in hand almost always works.