os·te·o·clast (?s?t?-?-kl?st?)n.1. A large multinucleate cell found in growing bone that resorbs bony tissue, as in the formation of canals and cavities.2. An instrument used in surgical osteoclasis.[osteo- + Medieval Latin -clast?s, breaker (from Late Greek -klast?s, from Greek klastos, broken, from kl?n, to break).]os?te·o·clas?tic adj.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.osteoclast (??st????klæst) n1. (Surgery) a surgical instrument for fracturing bone2. (Physiology) a large multinuclear cell formed in bone marrow that is associated with the normal absorption of bone ?osteo?clastic adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014os?te?o?clast (??s ti ??klæst) n. 1. a skeletal cell that functions in bone formation. 2. a surgical instrument for effecting osteoclasis. [1870?75; osteo- + -clast