Spelling can be very deceptive, so it wouldn’t be a surprise that if you saw this word written down “guai” it wouldn’t ring any bells. It’s a sort of teenage colloquialism, but one that’s been around for quite a while, meaning “cool” “great” “fab” “wicked” or whatever the latest one is. The trouble is it sounds exactly like “why?”
… or it least it did to me in my first year of teaching in Spain. I announced to a class: “Now we’re going to listen to close our books and listen to a song”. One of the kids whose name, Julián, I still remember said “guai”. “Well, because it’s good to have a change from time to time, and you can learn a lot of English for songs”. “No, I said ¡guai!” “As I said, because ….” this conversation went on for quite a while until Julián got up and wrote on the board GUAI – “It means I want to listen to a song!!”
Another word I never forgot again ….