Lewis Short
pernīcĭtas (noun F) : pernix
* Nimbleness, briskness, agility, swiftness, fleetness (class.): pernicitas deserit: consitus sum senectute,Plaut. Men. 5, 2, 4: adde pernicitatem et velocitatem,Cic. Tusc. 5, 15, 45; Caes. B. C. 3, 84: pedum pernicitas,Liv. 9, 16: homines saltatim currentes, vivacissimae pernicitatis,Gell. 9, 4, 9: equorum,Tac. H. 1, 79.
Charlton T. Lewis, Charles Short, A Latin Dictionary