four-o'clock \ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷\noun 1.: a plant of the genus Mirabilis: as a.: a common garden plant (M. jalapa) with fragrant yellow, red, or white flowers that open late in the afternoon — called also marvel-of-Peru b.: a California plant (M. laevis) with red flowers 2.[so called from its cry]: friarbird