'Mulch' definitions:

Definition of 'mulch'

noun

A protective covering of rotting vegetable matter spread to reduce evaporation and soil erosion

verb

Cover with mulch; "mulch the flowerbeds"

From: GCIDE

Mulch \Mulch\, n. [Cf. mull dirt, also Prov. G. mulsch, molsch, rotten, soft, mellow, as fruit.] Half-rotten straw, or any similar light, porous, organic substance strewn on the ground, as over the roots of plants, to protect from heat, drought, etc., and to hinder weed growth and preserve moisture. [1913 Webster]

From: GCIDE

Mulch \Mulch\, v. t. [imp. & p. p. Mulched; p. pr. & vb. n. Mulching.] To cover or dress with mulch. [1913 Webster]