Pronunciation: (rij'id),[key] —adj. 1. stiff or unyielding; not pliant or flexible; hard: a rigid strip of metal. 2. firmly fixed or set.
3. inflexible, strict, or severe: a rigid disciplinarian; rigid rules of social behavior. 4. exacting; thorough; rigorous: a rigid examination. 5. so as to meet precise standards; stringent: lenses ground to rigid specifications. 6. Mech.of, pertaining to, or noting a body in which the distance between any pair of points remains fixed under all forces; having infinite values for its shear modulus, bulk modulus, and Young's modulus.
7. Aeron. a. (of an airship or dirigible) having a form maintained by a stiff, unyielding structure contained within the envelope.
b. pertaining to a helicopter rotor that is held fixedly at its root.