diffuse vs riddle

diffuse is not a noun while riddle is a noun.

Word	Noun	Adjective	Verb	Adverb
diffuse	No	Yes	Yes	No
riddle	Yes	No	Yes	No

As verbs, diffuse and riddle are synonyms defined as:

Other synonyms of diffuse include imbue, interpenetrate, penetrate, permeate, pervade.

diffuse (noun)	riddle (noun)
	a coarse sieve (as for gravel)
	a difficult problem

diffuse (adjective)	riddle (adjective)
(of light) transmitted from a broad light source or reflected
spread out; not concentrated in one place
lacking conciseness

diffuse (verb)	riddle (verb)
cause to become widely known	explain a riddle
spread or diffuse through	set a difficult problem or riddle
move outward	speak in riddles
	pierce with many holes
	separate with a riddle, as grain from chaff
	spread or diffuse through