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.

---

'A' game British  

noun

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

---

Etymology

Origin of A game

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

Example Sentences

For the Kings, the season-high six goals comes at the end of a slide that had seen them lose six of their last seven, averaging less than two goals a game over that stretch.

From Los Angeles Times

Scot Anderson went 3-1 up in a game played at a ferocious pace, and was impressive in averaging 121 in set three.

From BBC

"It's no good for my age. It's hard, especially with Jermaine on you. What a game," Anderson told Sky Sports.

From BBC

“This type of project would be a game changer for downtown Dallas,” Welts said.

From The Wall Street Journal

But in a game previewing the quality of defenses the Chargers could face in the postseason, the offensive line — hit hard by the losses of Rashawn Slater and Joe Alt to injury — struggled to adequately protect Herbert.

From Los Angeles Times