Lewis & Short

percussĭo, ōnis, f. [percutio], a beating, striking (class.).

  1. I. Lit.: capitis percussiones, beatings on the head, Cic. Tusc. 3, 26, 62: digitorum, a snapping, id. Off. 3, 19, 75.
  2. II. Transf., in music and rhetoric, a beating time; hence, concr., time: percussiones numerorum, Cic. de Or. 3, 47, 182: percussionum modi, id. Or. 58, 198; Quint. 9, 4, 51; 11, 3, 108 al.