pi·ac·u·lar \(ˈ)pī|akyələ(r)\adjective Etymology: Latin piacularis, from piaculum + -aris -ar 1.: sacrificial, expiatory < required to make a piacular offering for their sins > 2.: requiring expiation : sinful, heinous < piacular offense > • pi·ac·u·lar·lyadverb • pi·ac·u·lar·nessnoun-es