(geology) the mechanical process of wearing or grinding something down (as by particles washing over it) WordNet 3.0

(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively Open English WordNet

Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Wikipedia

Gradual removal of a substance by chemical or mechanical means. Wikipedia Disambiguation

The general process or the group of processes whereby the materials of Earth's crust are loosened, dissolved, or worn away and simultaneously moved from one place to another, by natural agencies, which include weathering, solution, corrosion, and transportation, but usually exclude mass wasting. OmegaWiki

The breakdown of solid rock into smaller particles and its removal by water. OmegaWiki

Detachment and movement of topsoil or soil material from the upper part of the profile, by the action of wind or running water, especially as a result of changes brought about by human activity, such as unsuitable or mismanaged agriculture. OmegaWiki

The mechanical process of eroding or grinding. Wiktionary

Process of eroding or grinding. Wiktionary (translation)