Lewis & Short

vastĭtūdo, ĭnis, f. [vastus].

  1. I. = vastitas, II. A., ruin, destruction (ante-class.): Mars pater, te precorut tu morbos visos invisosque, viduertatem vastitudinemque, calamitates intemperiasque prohibessis, an old formula of prayer ap. Cato, R. R. 141, 2: quae vastitudo haec aut unde invasit mihi? Att. ap. Non. 184, 32 (Trag. Rel. v. 455 Rib.); Pac. ib. (Trag. Rel. v. 314 ib.).
  2. * II. = vastitas, II. B., fearful size, hugeness, immensity: corporis, Gell. 5, 14, 9.