Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
lăcūnārĭus, ii, m. [lacuna], a gravedigger (late Lat.), Firm. Math. 8, 21; cf.: lacunarius, λακκοπολός, Gloss. Philox.
lăcūno, āvi, ātum, 1, v. a. [lacuna].