sundial \ˈ ̷ ̷ˌ ̷ ̷ ̷ ̷\noun 1.: an instrument to show the time of day by the shadow of a gnomon on a usually horizontal plate or on a cylindrical surface 2.[so called from the fact that its leaves incline up to 90 degrees to follow the sun]: a common lupine (Lupinus perennis) of the eastern United States