ETYMOLOGY
variant of rampageous, after adjectives ending in -acious
EXAMPLE
“…In the main street of Ipswich, on the left-hand side of the way, a short distance after you have passed through the open space fronting the Town Hall, stands an inn known far and wide by the appellation of the Great White Horse, rendered the more conspicuous by a stone statue of some rampacious animal with flowing mane and tail, distantly resembling an insane cart-horse, which is elevated above the principal door…”
From: The Pickwick Papers
By Charles Dickens, 1836
Lexicophilia 