Lewis & Short

pĭācŭlum (sync. collat. form pĭā-clum, Prud. στεφ. 14, 219), i, n. [pio], a means of appeasing a deity; hence,

  1. I. Lit.
    1. A. A sin-offering, propitiatory sacrifiee: porco piaculo facito, Cato, R. R. 139; 140: porcc femina piaculum pati, to bring, Cic. Leg. 2, 22, 57: piaculum hostia caedi, Liv. 8, 10: te piacula nulla resolvent, Hor. C. 1, 28, 34: piacula manibus infert, Ov. M. 6, 569: falsi mundi, Liv. 1, 26: sed quo te, M. Tulli, piaculo taceam, i. e. how can I be justified in, etc., Plin. 7, 31, 31, § 116; Macr. S. 3, 10, 7.
      1. 2. Concr., an animal offered up in sacrifice, a victim: duc nigras pecudes; ea prima piacula sunto, Verg. A. 6, 153: non sperat tragicae furtiva piacula cervae, i. e. substitution, Juv. 12, 120.
        Transf.,
          1. (α) Of persons offered as an expiation, atonement: (Hannibalem) ad piaculum rupti foederis, Liv. 21, 10, 12: ut luendis periculis publicis piacula simus, id. 10, 28, 13.
          2. (β) In gen., a remedy, Hor. Ep. 1, 1, 36.
    2. B. Punishment: dea a violatoribus (sui templi) gravia piacula exegit, Liv. 29, 18; Just. 8, 2, 6; Val. Max. 1, 1, 14; Sil. 13, 702.
  2. II. Transf., that which requires expiation.
    1. A. A wicked action, sin, crime; guilt: eo die verberari piaculum est, Fab. Pict. ap. Gell. 10, 15, 10: palam mutire plebeio piaculum est, Enn. ap. Fest. s. v. mutire, p. 145 Müll. (Trag. v. 376 Vahl.): piaculum est misereri nos hominum rem male gerentum, Plaut. Truc. 2, 1, 13: sine piaculo rerum praetermissarum, Liv. 39, 47: piaculum committere, id. 5, 52; Paul. Sent. 1, 21, 4: commissa piacula, Verg. A. 6, 569: solutus piaculo, Tac. A. 1, 30: nec sine piaculo quodam sanctissimas necessitudines scindi, Plin. Pan. 37: ne terra impleatur piaculo, Vulg. Lev. 19, 29.
    2. B. An unhappy event, a misfortune, Plin. 25, 8, 46, § 84.