Lewis & Short

dē-rŭo, rŭi, 3, v. a. and n. (a very rare word).

  1. I. Act., to throw or cast down.
    1. A. Lit.: hiems immensam vim aquarum ruptis nubibus deruat, Sen. Q. N. 3, 27.
    2. B. Trop., to take away, detract: cumulum de laudibus alicujus, * Cic. Att. 16, 11, 2.
  2. II. Neutr., to fall down: Ap. M. 2, p. 128; 7, p. 196.