What is Check-swing?
1.
1. A type of swing in the game of baseball where the batter starts to swing for the ball, but stops the swing shortly before the ball reaches home plate. When deciding whether the swing was a check-swing rather than a full swing, the umpire presiding, with the optional aid of either the first or third base umpire, consider factors such as whether the bat passes the front of the plate or the batter pulls his wrists back.
2. When someone stops approaching another person, with the intention to flirt with them, after it becomes clear that he or she is not attracted to that person.
"Damn, that girl is hot...*starts approaching girl*...*gets a better look of girl*...ohhh, check-swing...*stops approaching girl*"
See