sperm whalen.1. A very large toothed whale (Physeter macrocephalus syn. P. catodon) formerly hunted for the spermaceti in its massive head and the ambergris in its intestines. Also called cachalot.2. Either of two small toothed whales (Kogia breviceps or K. sima) also containing spermaceti in the head.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.sperm whale n (Animals) a large toothed whale, Physeter catodon, having a square-shaped head and hunted for sperm oil, spermaceti, and ambergris: family Physeteridae. Also called: cachalot [C19: short for spermaceti whale]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014sperm? whale` n. a large, square-headed, toothed whale, Physeter catodon, having a cavity in the head that contains sperm oil and spermaceti. [1825?35] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.