irregular vs abnormal

irregular is a noun but abnormal is not a noun.

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

irregular (noun)	abnormal (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

irregular (adjective)	abnormal (adjective)
contrary to rule or accepted order or general practice	not normal; not typical or usual or regular or conforming to a norm
(of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement	departing from the normal in e.g. intelligence and development
(used of the military) not belonging to or engaged in by regular army forces	much greater than the normal
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