GNU Collaborative International Dictionary of English

Found one definition

1.       
   ‖Dipnoi (?), n. pl. [NL., fr. Gr.   with two breathing apertures; δι- = δίσ- twice +  breath.] (Zool.) A group of ganoid fishes, including the living genera Ceratodus and Lepidosiren, which present the closest approximation to the Amphibia. The air bladder acts as a lung, and the nostrils open inside the mouth. See Ceratodus, and Illustration in Appendix.
   
   [1913 Webster]