Sea elephant \Sea" el"e*phant\ (Zo["o]l.) A very large seal ({Macrorhinus proboscideus}) of the Antarctic seas, much hunted for its oil. It sometimes attains a length of thirty feet, and is remarkable for the prolongation of the nose of the adult male into an erectile elastic proboscis, about a foot in length. Another species of smaller size ({M. angustirostris}) occurs on the coast of Lower California, but is now nearly extinct.