(1) (General) The treatment of textile material in a bath of liquid, usually, although not necessarily, without agitation. The term is also applied to processes whereby the materials are impregnated with a liquor, highly squeezed, and then allowed to lie.
(2) In rayon manufacture, the process of immersing the dissolving pulp in a solution of sodium hydroxide (caustic soda) of mercerizing strength (17-20%). The purpose of this treatment is twofold: (a) to produce alkali-cellulose, and (b) to remove soluble impurities from the pulp. The operation is controlled by time and temperature.
(3) The process of retting flax straw by immersion in an aqueous liquor.
Textile Resource (http://www.textile.org.uk)