het·ero·cer·cal \| ̷ ̷ ̷ ̷ ̷ ̷|sərkəl\adjective Etymology:heter- + -cercal 1.: having the upper lobe larger than the lower with the end of the vertebral column prolonged and somewhat upturned in the upper lobe — used of the tail fin of various fishes (as sharks) 2.: having or relating to a heterocercal tail fin • het·ero·cer·cal·i·ty\|hed.ə(ˌ)rōˌsərˈkaləd.ē\noun-es