riff vs thumb

riff and thumb both are nouns.

Word	Noun	Adjective	Verb	Adverb
riff	Yes	No	Yes	No
thumb	Yes	No	Yes	No

As verbs, riff and thumb are synonyms defined as:

Other synonyms of riff include flick, flip, leaf, riffle.

riff (noun)	thumb (noun)
a jazz ostinato; usually provides a background for a solo improvisation	the part of a glove that provides a covering for the thumb
	a convex molding having a cross section in the form of a quarter of a circle or of an ellipse
	the thick short innermost digit of the forelimb

riff (verb)	thumb (verb)
play riffs	feel or handle with the fingers
look through a book or other written material	travel by getting free rides from motorists
	look through a book or other written material