cut·lass·fish (k?t?l?s-f?sh?)n. pl. cutlassfish or cut·lass·fish·es Any of several marine fishes of the genus Trichiurus and other genera of the family Trichiuridae, having a long, ribbonlike body and sharp teeth.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.