Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
incĭpisso (also incĭpesso), ĕre, v. a. [incipio], to begin (Plautin.): quid hic homo tantum incipissit facere cum tantis minis? Plaut. Capt. 4, 2, 22: nugas ineptiasque maxumas, id. ib. 3, 3, 17: magnam rem, id. Mil. 2, 2, 73: sic rationem, ib. 82: brevem orationem, id. Capt. 2, 1, 19; id. Trin. 4, 2, 42.