Lewis & Short

bacchātĭo, ōnis, f. [bacchor].

  1. I. A celebrating of the orgies of Bacchus, Hyg. Fab. 4; 8.
    Hence.
  2. II. A revelling, raving, in the manner of the Bacchœ (rare): sileatur de nocturnis ejus baccationibus ac vigiliis, * Cic. Verr. 2, 1, 12, § 33.