spread out vs diffuse

spread out is not an adjective while diffuse is an adjective.

Word	Noun	Adjective	Verb	Adverb
spread out	No	No	Yes	No
diffuse	No	Yes	Yes	No

As verbs, spread out and diffuse are synonyms defined as:

Other synonyms of spread out include fan out, spread.

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

spread out (verb)	diffuse (verb)
set out or stretch in a line, succession, or series	cause to become widely known
spread out or open from a closed or folded state	spread or diffuse through
move outward	move outward
extend in one or more directions
move away from each other
turn outward
strew or distribute over an area