1. 1. The condition of being unequal.
   2. An instance of being unequal.
2. 1. Lack of equality, as of opportunity, treatment, or status.
   2. Social or economic disparity: the growing inequality between rich and poor.
3. Lack of smoothness or regularity; unevenness.
4. Variability; changeability.
5. Mathematics. An algebraic relation showing that a quantity is greater than or less than another quantity.
6. Astronomy. A deviation from uniformity in the motion of a celestial body.

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.