ex·​os·​to·​sis ˌek-(ˌ)sä-ˈstō-səs How to pronounce exostosis (audio)
plural exostoses ˌek-(ˌ)sä-ˈstō-ˌsēz How to pronounce exostosis (audio)
: a spur or bony outgrowth from a bone or the root of a tooth

Example Sentences

Recent Examples on the Web An exostosis forms when the ears’ delicate tissues are repeatedly irritated over long periods of time. Nathaniel Scharping, Discover Magazine, 14 Aug. 2019 The dense growths are known as external auditory exostoses. Ashley Strickland, CNN, 14 Aug. 2019 Cold Water Love catching waves? Surfers and other cold water swimmers are prone to something called exostoses, or small bony growths in the ear canal that develop slowly over time and can prevent sound from getting in. Clare Thorp, Cosmopolitan, 2 Aug. 2017 Riley was born with a genetic condition called hereditary multiple exostoses (HME), which causes irregular bone growth. George Diaz, OrlandoSentinel.com, 4 July 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'exostosis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


New Latin, from Greek exostōsis, from ex out of + osteon bone — more at ex-, osseous

First Known Use

1736, in the meaning defined above

Time Traveler
The first known use of exostosis was in 1736

Dictionary Entries Near exostosis

Cite this Entry

“Exostosis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/exostosis. Accessed 21 Mar. 2023.

Medical Definition


ex·​os·​to·​sis ˌek-(ˌ)säs-ˈtō-səs How to pronounce exostosis (audio)
plural exostoses -ˌsēz How to pronounce exostosis (audio)
: a spur or bony outgrowth from a bone or the root of a tooth
exostotic adjective

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