n. [ Pref. di- + pyridine + -yl. ] (Chem.) A crystalline nitrogenous base, C10H8N2, obtained by the reduction of pyridine. [ 1913 Webster ]
n. [ Pyridine + -yl. ] (Chem.) A hypothetical radical, C5H4N, regarded as the essential residue of pyridine, and analogous to phenyl. [ 1913 Webster ]