Lewis Short
(adj.adv.) : monstrĭfĭcus, a, um, adj.monstrumfacio
* Monstrous, strange (post-Aug.): artes,i. e. magical,Val. Fl. 6, 152: natura hyaenae,Plin. 28, 8, 27, § 92: hominum ingenia,id. 21, 5, 13, § 26: effigies,id. 2, 3, 3, § 7; and so the better reading,Plin. 6, 30, 35, § 187; 36, 13, 19, § 88.—Hence, adv.: monstrĭfĭcē, in a monstrous or strange manner (post-Aug.), Plin. 28, 11, 49, § 181.
Charlton T. Lewis, Charles Short, A Latin Dictionary