OBR 2.00 · OBR 6.01(a)

Offensive interference

Interference is the offense illegally impeding the defense — a runner contacting a fielded ball, a batter stepping in front of the catcher's throw, a coach grabbing a runner. The penalty is almost always an out, a dead ball, and runners sent back.

Key points

Who interfered is usually who is out; intentional interference to break up a double play gets two outs.
The ball dies immediately — nothing that happens after the interference counts.
A fielder in the act of fielding a batted ball has the right of way; runners must avoid him.
Yelling to confuse a fielder is interference too — verbal interference is real, if rarely called.

In a game

Runner on first waves his arms crossing in front of the shortstop as a grounder arrives.

Ruling · Interference if the umpire judges he hindered the play — the runner is out, the ball is dead, the batter-runner is placed at first, and everyone else returns.

Why it moves the scoreboard

The harshest whistle in the sport: an out, a dead ball, and everyone sent back — rallies die on interference calls.