Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
observābĭlis, e, adj. [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.