diphenylaminePronunciation: /dʌɪˈfiːnʌɪləˌmiːn, -ˈfɛnɪl-/Definition of diphenylamine noun [mass noun] Chemistry a synthetic crystalline compound with basic properties, used in making azo dyes and as an insecticide and larvicide. Chemical formula: (C6H5)2NH diphenylamine in other Oxford dictionaries Definition of diphenylamine in the US English dictionary