A baseball term that refers to a situation in which a pitcher throws a pitch for a strike that is unanticipated or deceptive, causing the batter to fail to swing at it.
While a pitcher might "freeze a hitter" with any pitch, batters are typically frozen by pitches as the final strike of an at bat. Most often, pitches that freeze hitters are off-speed pitches (e.g. curveball, changeup) or fastballs that touch a corner of the strike zone. Pitchers will often set up hitters with pitches out of the strike zone, causing them to anticipate a similar location, and then change the pitch to catch them off guard, thus "freezing" them for the final strike.