Soil \Soil\, v. t. [imp. & p. p. Soiled; p. pr. & vb. n. Soiling.]

[OF. saoler, saouler, to satiate, F. so[^u]ler, L. satullare, fr. satullus, dim. of satur sated. See Satire.]

To feed, as cattle or horses, in the barn or an inclosure, with fresh grass or green food cut for them, instead of sending them out to pasture; hence (such food having the effect of purging them), to purge by feeding on green food; as, to soil a horse.

Source: Webster's Revised Unabridged Dictionary (1913)