co·pa·cet·ic or co·pa·set·ic (k??p?-s?t??k)adj. Informal Very satisfactory or acceptable; fine.[Origin unknown.]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.copacetic (?k??p??s?t?k) , copasetic , copesetic or copesetticadjslang US and Canadian very good; excellent; completely satisfactory[C20: of unknown origin]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014co?pa?cet?ic or co?pa?set?ic (?ko? p??s?t ?k, -?si t?k) adj. Slang. completely satisfactory. [1915?20; of obscure orig.] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.