Ahhh ... the cry of doom (or triumph) heard at the end of every tennis match. But hark! It can be heard outside tennis! It has an idiomatic meaning! Who knew?
OK, me ...
I know. Life's full of surprises and I like surprising people.
Meaning (idiomatic, of course) and EtymologyEdit
This one's pretty obvious - it means game over. And I guess its main use would be gloating, unless you're a really good sport ...
It also refers to the point that wins an argument ("Game, set and match!" is always yelled after a match point. Or a championship point, if it's a final).
Use in Normal SpeechEdit
(and I am not referring to umpires here)
"Ha! Game, set and match to me! You shouldn't have said you were sure you'd win!"
If you're being really nice and admitting defeat.
"OK. You win. Game, set and match to you."
If you've just won an argument and are therefore gloating.
"Gotcha. So I'm right! Game, set an match to me!"