Definition of: hydrocyanic

(hī′drō·sī·an′ik) adjective Chem.
Of, pertaining to, or designating an unstable, volatile, colorless, and extremely poisonous acid, HCN, formed by decomposing metallic cyanides with hydrochloric acid. It is only slightly dissociated in water, and has a characteristic odor resembling that of bitter almonds: also called prussic acid.