1. 1. The act or an instance of hindering, obstructing, or impeding.
   2. Something that hinders, obstructs, or impedes.
2. 1. Sports. Illegal obstruction or hindrance of an opposing player, such as hindrance of a receiver by a defender in football, hindrance of a fielder by a base runner in baseball, or checking a player not in possession of the puck in ice hockey.
   2. Football. The legal blocking of defensive tacklers to protect and make way for the ball carrier.
3. Physics. The variation of wave amplitude that occurs when waves of the same or different frequency come together.
4. Electronics.
   1. The inhibition or prevention of clear reception of broadcast signals.
   2. The distorted portion of a received signal.
5. The negative or distorting effect that new learning can have on previous learning or that previous learning can have on new learning.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.