thickening

Short definition from Wiktionary

Noun

1. 1
   The process of making something, or becoming, thick or viscous.
2. 2
   A substance, usually a source of starch, used to thicken a sauce.
3. 3
   A thickened part of a structure.

Verb

1. 1
   present participle and gerund of thicken

Adjective

1. 1
   Beginning to thicken, becoming thicker.