1. 1. Opposite: antimere.
   2. Opposing; against: antiapartheid.
   3. Counteracting; neutralizing: antacid.
   4. Destroying: antiaircraft.
2. 1. Inverse: antilogarithm.
   2. Displaying opposite characteristics: antihero.

[Greek, from anti, opposite.]

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.