Thing To Be Today: chuffed.

According to the Collins dictionary, this word is only used in Britain. It's marked as slang, as well, but it's still a lovely word for a lovely thing, and I don't see why anyone who likes it shouldn't borrow it.

People are usually either dead chuffed or well chuffed or none too chuffed.

What does it mean? 

It means pleased and delighted, but there's also a sense of being just a bit pleased with oneself, as well: of being a bit more confident, of walking a bit taller, of being a bit more out-going.

You can be pleased without smiling, but to be chuffed shows in a beaming smile and a bit of a swagger.

Etymologically, the smile is important.

Thing To Be Today: chuffed. This word meant chubby before it meant pleased, and before that, in the 1500s, a chuff was a fat cheek (as one has when one smiles).

Strangely, though I've never come across it in real life, there's another word chuff, which might come from the same source, and which means sullen. This seems to have at root the same kind of idea - basically, fat-headed or thick.