attrition Definition

attrition
noun

1. A rubbing together; friction.
2. military.
A relentless wearing down of an enemy's strength, morale, etc, especially by continual attacks.
Example: war of attrition
3. geol.
The process whereby rock fragments become worn, smooth and smaller in size while being transported by water, wind or gravity.

Etymology: 14c: from Latin attritio, from atterere to rub.