In baseball what is a walk off hit?

Answer 1

A Walk-Off hit is any hit that occurs at the bottom of the 9th inning (or beyond the 9th if game goes into extra innings) which results in a run or runs scored that will give the lead (and thus the win) to the hitting team. In other words, it's a hit that ends the game and thus the players can walk-off the field.

Answer 2

a walk off base hit is when a batter gets a base hit(single, double, triple) which scores a run in a tie ball game that ends the game immediately. Walk-off means the team walks off the field because the game is over as soon as the player gets the hit.