Weathering

Weath′er-ing

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Noun.

(Geol.)

The action of the elements on a rock in altering its color, texture, or composition, or in rounding off its edges.

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ppr.

Passing or sailing to the windward; passing with difficulty.

weathering ‎(countable and uncountable, plural weatherings)

(obsolete) Weather, especially favourable or fair weather.
(geology) Mechanical or chemical breaking down of rocks in situ by weather or other causes.
(architecture) A slight inclination given to an approximately horizontal surface to enable it to throw off water.

breaking down of rocks

weathering