Entry 1 sense Webster, 1913 Lungfish /lŭng'-fĭshˌ/ · Lung·fish · IPA /lˈʌŋfˌɪʃ/ 01 n. Any fish belonging to the Dipnoi; -- so called because they have both lungs and gills. 1. Any fish belonging to the Dipnoi; -- so called because they have both lungs and gills.(Zool.)