Lewis & Short

ag-grăvesco (adg-), ĕre, 3, v. inch., to become heavy.

  1. I. Lit.: propinquitate parti, Pac. ap. Non. 486, 5 (Trag. Rel. p. 85 Rib.).
  2. II. Fig., of sickness, to become violent, severe, dangerous: ne Philumenae magis morbus adgravescat, grow worse, be aggravated, Ter. Hec. 3, 2, 2.