sail·fish (s?l?f?sh?)n. pl. sailfish or sail·fish·es Either of two large marine fishes, Istiophorus albicans of the Atlantic Ocean or I. platypterus of the Indian and Pacific Oceans, having a large saillike dorsal fin and an elongated, spearlike upper jaw.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.sailfish (?se?l?f??) n, pl -fish or -fishes1. (Animals) any of several large scombroid game fishes of the genus Istiophorus, such as I. albicans (Atlantic sailfish), of warm and tropical seas: family Istiophoridae. They have an elongated upper jaw and a long sail-like dorsal fin2. (Animals) another name for basking sharkCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014sail?fish (?se?l?f??) n., pl. (esp. collectively) -fish, (esp. for kinds or species) -fish?es. either of two large marlinlike fish of the genus Istiophorus, distinguished by a long, high dorsal fin and a swordlike snout. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.