1. (noun)blackjack oak, blackjack, jack oak, Quercus marilandica a common scrubby deciduous tree of central and southeastern United States having dark bark and broad three-lobed (club-shaped) leaves; tends to form dense thickets
2. (noun)jack oak, northern pin oak, Quercus ellipsoidalis small to medium deciduous oak of east central North America; leaves have sharply pointed lobes