A 100 yard game is a reference to an offensive player gaining 100 yards during the course of a game. It could refer to a defensive player who had a particularly good day returning turnovers for touchdowns, but not usually. The term most often applies to running backs and other rushers, and receivers.
The record for most 100 yard rushing games in the NFL belongs to Emmitt Smith (78), while Barry Sanders owns the record for most 100 yard rushing games in a season with 14 in 1997. The record for most 100 yard reception games in a season belongs to Michael Irvin, who had 11 such games in 1995. The career record belongs to Hall of Famer Jerry Rice, who had 78 during the course of his career. There are no notable records for 100 yard passing games because most quarterbacks tally more than 100 yards passing in every game.