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

Included in the deal will be a “Banana Ball Day” at Disneyland and a game at Angel Stadium on March 26.

From Los Angeles Times

Stewart said they met again by chance at a game fair in the summer of 1995, when they passed each other in an aisle.

From BBC

Hearts are four points clear of second-placed Rangers and six ahead of third-placed Celtic, who have a game in hand.

From Barron's

“He’s an incredible talent who has an awesome ceiling, and he’s got an incredible future. But in a game like tonight — he’s learning. You can see it out there. He’s learning on the fly.”

From Los Angeles Times

With tickets in the away end sold to Swansea supporters, this was a record number of home fans at a game in this stadium.

From BBC