1 definition by The_Post_Man

A mocking neg used in sports/ games against an opponent that just made an unforced error that greatly helped you or your team.

The phrase suggests that the error was actually intentional and they were attempting to "take a dive" to receive payment.
In Sports (Baseball):
*Thrown ball tips off of first basemen's glove and flies off into foul territory*

Runner as they round first heading for second: "Check's in the mail!"

Video Game (Any MOBA)
*Opponent uses an ability to grab and pull you away from a deadly situation, allowing you to use a movement ability to escape there after*

All Chat: "Check's in the mail!"
by The_Post_Man March 19, 2021
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