Lewis Short
(adjective) : observābĭlis, e, observo
* Remarkable, observable (post-Aug.): manus,Quint. 9, 1, 20: patientia,remarkable,App. M. 11, p. 267, 8: nox ista est observabilis Domini,Vulg. Exod. 12, 42.
Charlton T. Lewis, Charles Short, A Latin Dictionary