li·thi·a·sis (l?-th???-s?s)n. pl. li·thi·a·ses (-s?z?) Pathological formation of mineral concretions in the body.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.lithiasis (l???a??s?s) n (Pathology) pathol the formation of a calculus[C17: New Latin; see litho-, -iasis]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014li?thi?a?sis (l???a? ? s?s) n. the formation or presence of stony concretions in the body. [1650?60;