hydroquinonePronunciation: /ˌhʌɪdrəˈkwɪnəʊn/Definition of hydroquinone noun [mass noun] Chemistry a crystalline compound made by the reduction of benzoquinone. Alternative name: benzene-1,4-diol; chemical formula: C6H4(OH)2 hydroquinone in other Oxford dictionaries Definition of hydroquinone in the US English dictionary