Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĭn-errābĭlis, e, adj. [2. in-erro], unerring (post-class.): meatus, App. Dogm. Plat. 1, p. 7, 27: orbis, id. de Mundo, p. 58, 6: computatio, August. Civ. Dei, 21, 8.