From BR Bullpen
Defensive Indifference is a play in the later stages of a game in which the defensive team, either ahead or behind by a large amount allows a player to advance a base without any attempt to put the runner out.
The play may be ruled, by the official scorer, defensive indifference.
The most common situation for defensive indifference is when a runner on first base advances to second base as the pitch is delivered. This would normally be regarded as a stolen base attempt, but is instead scored as defensive indifference if the defense makes no play, and that runner scoring would not affect the outcome of the game.