jackknife-fish

[jak-nahyf-fish]
noun, plural jack·knife-fish·es, (especially collectively) jack·knife-fish. Ichthyology.
  1. a black and white, American drum, Equetus lanceolatus, found in tropical areas of the Atlantic Ocean, having an elongated dorsal fin that is held erect.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018