cachinnation Also found in: Thesaurus, Medical . Related to cachinnation: cachinnating, cachinnator cach·in·nate (kăk′ə-nāt′) intr.v. cach·in·nat·ed, cach·in·nat·ing, cach·in·nates To laugh hard, loudly, or convulsively; guffaw. [Latin cachinnāre, cachinnāt-, of imitative origin.] cach′in·na′tion n. cach′in·na′tor n. 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. cachinnation (ˌkækɪˈneɪʃən) n 1. raucous laughter 2. (Psychiatry) psychiatry inappropriate laughter, sometimes found in schizophrenia Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011,...