hydroxyapatitePronunciation: /ˌhʌɪdrɒksɪˈapətʌɪt/Definition of hydroxyapatite noun [mass noun] a mineral related to apatite which is the main inorganic constituent of tooth enamel and bone, although it is rare in rocks. hydroxyapatite in other Oxford dictionaries Definition of hydroxyapatite in the US English dictionary