ammoniac n the aromatic gum of the ammoniac plant a pertaining to or containing or similar to ammonia Usage(s) Two University of Brussels chemists have since produced sal-ammoniac gas in their laboratory, using the computer data for guidance. Stars prick the eyes with sharp ammoniac proverbs, New verities, new inklings in the velvet hummed . Siegel and his associates incubated the soil in a hostile ammoniac atmosphere, and fed it with a nutrient broth. Synonym(s) gum ammoniac ammoniacal