milleritePronunciation: /ˈmɪlərʌɪt/Definition of millerite noun [mass noun] a mineral consisting of nickel sulphide and typically occurring as slender needle-shaped bronze crystals. Origin: mid 19th century: named after William H. Miller (1801–80), English scientist, + -ite1millerite in other Oxford dictionaries Definition of millerite in the US English dictionary