irregular

contrary to rule or accepted order or general practice

“irregular hiring practices”

not occurring at a regular rate or fixed intervals

“an irregular heartbeat”

(used of the military) not belonging to or engaged in by regular army forces

“irregular troops”

“irregular warfare”

(of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement

failing to meet a standard of manufacture due to an imperfection

“an irregular pair of jeans”

deviating from normal expectations; somewhat odd, strange, or abnormal

“these days large families are atypical”

“atypical clinical findings”

“atypical pneumonia”

“highly irregular behavior”

a member of an irregular armed force that fights a stronger force by sabotage and harassment

merchandise that has imperfections; usually sold at a reduced price without the brand name