Lewis & Short

cŏactor, ōris, m. [cogo].

  1. I. Prop.
    1. A. A collector of money (from auctions, of revenues, etc.), Cato, R. R. 150, 2; Cic. Clu. 64, 180; id. Rab. Post. 11, 30; * Hor. S. 1, 6, 86; cf. Acron. and Porphyr. in h. l. and Auct. Vit. Hor. 1; Sen. Ep. 81, 2 (al. decoctor).
    2. B. Coactores agminis, the rear, Tac. H. 2, 68.
    3. C. ( = coactiliarius.) A fuller, Inscr. Grut. 648, 3.
  2. II. Trop., one who forces to something: adjutor, et, ut ita dicam, coactor, Sen. Ep. 52, 4.