A game

American  

Or A-game,

noun

Informal.

1. a person’s best effort, abilities, or achievement.

   The candidate brought her A game to the debate.

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'A' game British  

noun

1. informal one's best possible performance, esp in the phrase to bring or take one's 'A' game

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Etymology

Origin of A game

In reference to a sports contest, with the letter A indicating peak performance

Example Sentences

Villa are playing well right now but this is a tough trip for them and with their heavy schedule it might be a game too far.

From BBC

I can see them losing a game or two then, but only if anyone is still close to them.

From BBC

During a game, competitors are given files of jumbled data and scenarios or 'cases' that require sorting, based on a question, within the quickest time.

From BBC

Mr Irvine said that the vaccination has not been widely taken up by farmers and is "quite expensive," but added that this is a "game changer now".

From BBC

The Lakers have a game Monday against the visiting Phoenix Suns, but it’s unclear if James will play.

From Los Angeles Times