Lewis Short
(adjective) : pȳgĭsĭăcus, a, um, πυγησιακός (not in use), from πυγή, qs.
* Of or belonging to secret buttock-worship: puellam invitare ad pygisiaca sacra,i. e. to copulation,Petr. S. 140 (al. pygiaca, pygiciaca, in the same signif.).
Charlton T. Lewis, Charles Short, A Latin Dictionary