verb (used with or without object)
- to make or become thick or thicker.
- to make or grow more intense, profound, intricate, or complex: The plot thickens.
- to make or become thick or thickerthicken the soup by adding flour
- (intr) to become more involvedthe plot thickened
v.early 15c. (transitive), 1590s (intransitive), from thick + -en (1). Related: Thickened; thickening. An earlier verb was Old English þiccian.