(dentistry, automotive, informal) Nitrous oxide.

(automotive, informal) The system in some racing vehicles which pumps nitrous oxide into the engine to improve performance.

(now historical) Pertaining to or composed of nitre; having the properties of nitre, bitter.

(chemistry) Of, relating to, or derived from nitrogen, especially in which the valence of the nitrogen is lower than that of a corresponding nitric species.

(chemistry) Of or relating to nitrous acid or its derivatives.

(mycology, biology) Having a sharp odor like ammonia or nitric acid.