ultralightEnglishOxford New American Dictionaryultralight ▸ adjective /ˈəltrəlīt, ˈəltrəlaɪt / extremely lightweight: an ultralight notebook computer. ▸ noun /ˈəltrəlīt, ˈəltrəlaɪt / mainly North American a small, light, single-seater aircraft: he has taken to flying ultralights [as modifier] ultralight aircraft.