osteoporosis Syllabification: (os·te·o·po·ro·sis)Pronunciation: /ˌästēōpəˈrōsis/Translate osteoporosis | into German | into Italian Definition of osteoporosis noun a medical condition in which the bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes, or deficiency of calcium or vitamin D. Derivatives osteoporoticPronunciation: /-ˈrätik/ adjective Origin: mid 19th century: from osteo- 'bone' + Greek poros 'passage, pore' + -osisosteoporosis in other Oxford dictionaries Definition of osteoporosis in the British & World English dictionary