geranialPronunciation: /dʒɪˈreɪnɪəl/Definition of geranial noun [mass noun] Chemistry a fragrant oil present in lemon grass oil and used in perfumery. An isomer of citral; chemical formula: C10H16O Origin: late 19th century: from German, contraction of Geraniumaldehydegeranial in other Oxford dictionaries Definition of geranial in the US English dictionary