Checkmate is a chess term used when the opponent cannot move their king out of check. Checkmate doesnt just mean that you've simply cornered the enemy king its a declarationthat the enemy king is yours.
What you say when someone has been burnt/roasted. When there's just nocoming back, and they have nothing to say in reply. There are no moves remaining.
Sid: Chris, would you mind using at least one of your two brains cells to help me out here?
Chris: aTleAsT I hAvE a BrAiN.
Rithana: Ooof, checkmate.