fos·sa 1 (f?s??)n. pl. fos·sae (f?s???) Anatomy A small cavity or depression, as in a bone.[Latin, ditch, from feminine past participle of fodere, to dig.]fos?sate? (f?s??t?) adj.fos·sa 2 (f?s??)n. A catlike carnivorous mammal (Cryptoprocta ferox) of Madagascar, having reddish-brown fur, a long tail, long whiskers, and retractile claws.[Malagasy fosa.]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.fossa (?f?s?) n, pl -sae (-si?) (Anatomy) an anatomical depression, trench, or hollow area[C19: from Latin: ditch, from fossus dug up, from fodere to dig up]fossa (?f?s?) n (Animals) a large primitive catlike viverrine mammal, Cryptoprocta ferox, inhabiting the forests of Madagascar: order Carnivora (carnivores). It has thick reddish-brown fur and preys on lemurs, poultry, etc[from Malagasy]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014fos?sa1 (?f?s ?) n., pl. fos?sae (?f?s i) a pit, cavity, or depression, as in a bone. [1820?30;