'Thinning' definitions:

Definition of 'thinning'

From: WordNet
noun
The act of diluting something; "the cutting of whiskey with water"; "the thinning of paint with turpentine" [syn: cutting, thinning]

Definition of 'Thinning'

From: GCIDE
  • Thin \Thin\, v. t. [imp. & p. p. Thinned; p. pr. & vb. n. Thinning.] [Cf. AS. ge[thorn]ynnian.] To make thin (in any of the senses of the adjective). [1913 Webster]