Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cantillo, āvi, ātum, 1, v. dim. a. [canto], to sing low, to hum (post-class.; perh. only in App.), App. M. 4, p. 146; id. Flor. 1, p. 342, 8; 3, p. 388, 13 al.