What is "fallowing"

Fallow \Fal"low\, v. t. [imp. & p. p. Fallowed; p. pr. & vb. n. Fallowing.] [From Fallow, n.] To plow, harrow, and break up, as land, without seeding, for the purpose of destroying weeds and insects, and rendering it mellow; as, it is profitable to fallow cold, strong, clayey land.

n. A period during which a field is left fallow. vb. (present participle of fallow English)