famotidine /fəˈmoʊ.tɪˌdin/ noun1 •An H₂ antagonist C₈H₁₅N₇O₂S₃ (trademark Pepcid) used to inhibit gastric acid secretion especially in the short-term treatment of gastric and duodenal ulcers and gastroesophageal reflux disease and in the treatment of disorders (as Zollinger–Ellison syndrome) involving gastric acid hypersecretion.