Noun

• S: (n) guerrilla, guerilla, irregular, insurgent (a member of an irregular armed force that fights a stronger force by sabotage and harassment)
• S: (n) irregular, second (merchandise that has imperfections; usually sold at a reduced price without the brand name)

Adjective

• S: (adj) irregular (contrary to rule or accepted order or general practice) "irregular hiring practices"
• S: (adj) irregular, unpredictable (not occurring at a regular rate or fixed intervals) "an irregular heartbeat"
• similar to
• S: (adj) sporadic (recurring in scattered and irregular or unpredictable instances) "a city subjected to sporadic bombing raids"
• derivationally related form
• antonym
• S: (adj) irregular ((used of the military) not belonging to or engaged in by regular army forces) "irregular troops"; "irregular warfare"
• S: (adj) irregular ((of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement)
• S: (adj) irregular (failing to meet a standard of manufacture due to an imperfection) "an irregular pair of jeans"
• S: (adj) atypical, irregular (deviating from normal expectations; somewhat odd, strange, or abnormal) "these days large families are atypical"; "atypical clinical findings"; "atypical pneumonia"; "highly irregular behavior"
• S: (adj) irregular, temporary (lacking continuity or regularity) "an irregular worker"; "employed on a temporary basis"
• similar to
• derivationally related form
• antonym
• S: (adj) irregular ((of a surface or shape); not level or flat or symmetrical) "walking was difficult on the irregular cobblestoned surface"
• S: (adj) irregular, maverick, unorthodox (independent in behavior or thought) "she led a somewhat irregular private life"; "maverick politicians"