(grammar) describing a word that is not formed in the usual way

dive into the water bending the body at the waist at a right angle, like a jackknife

(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

failing to meet a standard of manufacture due to an imperfection

lacking continuity or regularity

independent in behavior or thought

(of a surface or shape); not level or flat or symmetrical

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