[di.a.base] n [F, prob. fr. Gk diabasis act of crossing over, fr. diabainein to cross over, fr. dia- + bainein to go--more at come] (ca. 1816) 1 archaic: diorite
2. chiefly Brit: an altered basalt
3: a fine-grained rock of the composition of gabbro but with an ophitic texture -- di.a.ba.sic adj