unrhythmical vs irregular

unrhythmical is not a noun while irregular is a noun.

Word	Noun	Adjective	Verb	Adverb
unrhythmical	No	Yes	No	No
irregular	Yes	Yes	No	No

unrhythmical (noun)	irregular (noun)
	merchandise that has imperfections; usually sold at a reduced price without the brand name
	a member of an irregular armed force that fights a stronger force by sabotage and harassment

unrhythmical (adjective)	irregular (adjective)
not rhythmic; irregular in beat or accent	contrary to rule or accepted order or general practice
	(of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement
	(used of the military) not belonging to or engaged in by regular army forces
	deviating from normal expectations; somewhat odd, strange, or abnormal
	failing to meet a standard of manufacture due to an imperfection
	lacking continuity or regularity
	not occurring at a regular rate or fixed intervals
	independent in behavior or thought
	(of a surface or shape); not level or flat or symmetrical