A grand slam occurs when a batter hits a home run with men on first base, second base and third base. Four runs score on a grand slam -- the most possible on one play -- and a batter is awarded four RBIs.
Understandably, a grand slam usually has an immense impact on the result of the game, because four runs score on the play. It's relatively rare to see a team win after allowing a grand slam. When a team trails by four runs or fewer, announcers will often say the team is "within slam range" because it could tie the game or take the lead with a grand slam.
Grand slams are incredibly rare. They are also entirely a result of the circumstances, meaning some of the game's greatest sluggers haven't hit many grand slams simply because the situation (three men on base) doesn't present itself often.
The term originated in the card game Bridge, referring to a player winning every trick. It carried over into baseball because it refers to a team scoring as many runs as possible in one at-bat.
Watch: Kris Bryant hits a grand slam.
In A Call
"slam," "salami," "grand salami," "grand-slam home run"