1. A sudden or violent backward whipping motion.
2. An antagonistic reaction to a trend, development, or event: "As the backlash against divorce progressed, state legislatures . . . called for a rollback of no-fault divorce laws and even for premarital waiting periods" (Walter Kirn).
3. A snarl formed in the part of a fishing line that is wound around the reel.
4. The play resulting from loose connections between gears or other mechanical elements.

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.