Definition of "piacular"

And while we think it ſo piaculous, to go beyond the Ancients; we muſt neceſſarily come ſhort of genuine Antiquity, Truth; unleſs we ſuppoſe them to have reach'd perfection of Knowlege in ſpight of their own acknowledgments of Ignorance.

1665, Joseph Glanvill, Scepsis Scientifica: or, Contest Ignorance, the way to Science […], London: […], Chapter XVII, page 103

The piacular sacrifice arose from the need of atoning for bloodshed within the kinship group ; properly speaking, the culprit himself should suffer : should he be unknown or beyond the reach of vengeance, a substitute had to be found […]

1911, Hugh Chisholm, The Encyclopædia Britannica: A Dictionary of Arts, Sciences, Literature and General Information, page 981

The distinction between clean and unclean beasts and birds was made, a distinction which has its principal significance in reference to a piacular offering. Not any and everything may be offered as an atonement, but only that which is [clean].

2013 November 25, W.G.T. Shedd, Dogmatic Theology, Ravenio Books