ASA - INTERFERENCE: The act of an offensive player or team member, umpire or spectator
that impedes, hinders, or confuses a defensive player attempting to execute a
play. Contact is not necessary.
USSSA - INTERFERENCE. Interference is an act which interferes with, obstructs, impedes,
hinders or confuses any fielder attempting to make a play.
A. Offensive interference is interference (physical or verbal) by the team at
bat, or when a runner creates malicious contact with any fielder with or
without the ball, in or out of the baseline; or when a coach physically
assists a runner during playing action.
NSA - INTERFERENCE. Interference is the act of an offensive player or team member, who
impedes or confuses a defensive player while attempting to execute a play. If judged so by
the umpire, vocal interference may be called.
FED/PGF - Interference is an act (physical or verbal) by a member of the team at bat who illegally impedes, hinders or confuses any fielder; or when a runner creates malicious contact with any fielder with or without the ball, in or out of the baseline.
I have always found it interesting that the rules are written this way yet I have never seen any base runner called out for stalling in front of a ground ball and intentionally making it difficult for an infielder to see the ball coming, then jumping over the ball at the last second and proceeding to the next base. I've seen quite a few errors by infielders as a result of this practice, however.