1. Displaying or marked by a lack of consistency, especially:
   1. Not regular or predictable; erratic: inconsistent behavior.
   2. Lacking in correct logical relation; contradictory: inconsistent statements.
   3. Not in agreement or harmony; incompatible: an intersection inconsistent with the road map.
2. Mathematics. Not solvable for the unknowns by the same set of values. Used of two or more equations or inequalities.

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.