osteosclerosis

noun
os·​teo·​scle·​ro·​sis | \ -sklə-ˈrō-səs How to pronounce osteosclerosis (audio) \
plural osteoscleroses\ -​ˌsēz How to pronounce osteoscleroses (audio) \

Medical Definition of osteosclerosis

: abnormal hardening of bone or of bone marrow