undemocratic vs authoritarian

undemocratic is not a noun while authoritarian is a noun.

Word	Noun	Adjective	Verb	Adverb
undemocratic	No	Yes	No	No
authoritarian	Yes	Yes	No	No

undemocratic (noun)	authoritarian (noun)
	a person who behaves in a tyrannical manner

undemocratic (adjective)	authoritarian (adjective)
not in agreement with or according to democratic doctrine or practice or ideals	expecting unquestioning obedience
	characteristic of an absolute ruler or absolute rule; having absolute sovereignty