antepaenultimus

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.

antĕ-paenultĭmus (less correctly written -pēn-), a, um, adj.;

in gram., pertaining to the third syllable from the end , antepenultimate , Diom. p. 425 P.; Mart. Cap. 3, p. 60 al.