haematemesisPronunciation: /ˌhiːməˈtɛmɪsɪs/ (US hematemesis)Definition of haematemesis noun [mass noun] Medicine the vomiting of blood. Origin: early 19th century: from haemato- 'of blood' + Greek emesis 'vomiting'haematemesis in other Oxford dictionaries Definition of haematemesis in the US English dictionary