The Collaborative International Dictionary of English v.0.48:

Fescennine \Fes"cen*nine\, a. [L. Fescenninus, fr. Fescennia, a
   city of Etruria.]
   Pertaining to, or resembling, the Fescennines. -- n. A style
   of low, scurrilous, obscene poetry originating in fescennia.
   [1913 Webster]