pros·the·sis (pr?s-th??s?s)n. pl. pros·the·ses (-s?z) 1. An artificial device used to replace a missing body part, such as a limb, tooth, eye, or heart valve.2. Replacement of a missing body part with such a device.3. Linguistics Prothesis.[Greek, addition, from prostithenai, prosthe-, to add : pros-, pros- + tithenai, to put; see dh?- in Indo-European roots.]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.prosthesis (?pr?s??s?s; pr?s??i?s?s) n, pl -ses (-?si?z) 1. (Surgery) surgery a. the replacement of a missing bodily part with an artificial substituteb. an artificial part such as a limb, eye, or tooth2. (Phonetics & Phonology) linguistics another word for prothesis[C16: via Late Latin from Greek: an addition, from prostithenai to add, from pros- towards + tithenai to place] prosthetic adj pros?thetically advCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014pros?the?sis (pr?s??i s?s for 1; ?pr?s ?? s?s for 2 ) n., pl. -ses (-siz for 1; -?siz for 2 ) 1. a device, either external or implanted, that substitutes for or supplements a missing or defective part of the body. 2. prothesis (def. 1). [1545?55;