Entry 1 sense Webster, 1913 Addax · Ad·dax · IPA /ˈa.daks/ 01 n. One of the largest African antelopes (Hippotragusnasomaculatus [or] Oryx nasomaculatus). 1. One of the largest African antelopes (Hippotragusnasomaculatus [or] Oryx nasomaculatus).(Zool.)