What is a interferer?

Answer 1

By any chance do you mean Interference? This term would apply to Automobiles and to Baseball, the categories you listed this question in. In an automobile engine the term interference describes an Interference engine which is a type of internal combustion engine where in the event of a serious valve train failure, or a 180 degree timing error, could lead the valves and pistons to strike each other. The most common cause of this a broken timing belt, but a catastrophic timing chain failure can also bring about this situation.

In baseball, interference is an infraction where a person illegally changes the course of play from what is expected. Interference might be committed by players on the offense, players not currently in the game, catchers, umpires, or spectators; each type of interference is covered differently by the rules.