- An aromatic organic base, C<sub>9</sub>H<sub>7</sub>N, having a pungent tarlike odor, synthesized or obtained from coal tar, and used as a food preservative and in making antiseptics, drugs, and dyes.
- Same as <internalXref urlencoded="chinoline">chinoline</internalXref>.
- A nitrogenous base, C9H7N obtained as a pungent colorless liquid by the distillation of alkaloids, bones, coal tar, etc. It the nucleus of many organic bodies, especially of certain alkaloids and related substances; hence, by extension, any one of the series of alkaloidal bases of which quinoline proper is the type.
- Any of a <xref>class</xref> of <xref>aromatic</xref> <xref>heterocyclic</xref> <xref>compounds</xref> containing a <xref>benzene</xref> <xref>ring</xref> <xref>fused</xref> with a <xref>pyridine</xref> ring; especially the <xref>simplest</xref> such compound, C9H7N.