frustrate vs dun

frustrate is not a noun while dun is a noun.

Word	Noun	Adjective	Verb	Adverb
frustrate	No	No	Yes	No
dun	Yes	Yes	Yes	No

As verbs, frustrate and dun are synonyms defined as:

Other synonyms of frustrate include bedevil, crucify, rag, torment.

frustrate (noun)	dun (noun)
	horse of a dull brownish grey color
	a color or pigment varying around a light grey-brown color

frustrate (adjective)	dun (adjective)
	of a dull greyish brown to brownish grey color

frustrate (verb)	dun (verb)
treat cruelly	make a dun color
hinder or prevent (the efforts, plans, or desires) of	cure by salting
	persistently ask for overdue payment
	treat cruelly