Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
lallo, āvi, ātum, 1, v. n., to sing lalla or lullaby, to sing as a nurse to a child: iratus mammae, lallare recusas, will not let yourself be sung to sleep, Pers. 3, 17; Hier. Ep. 14, 3: lallare βαβάζειν, Gloss. Philox.