Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cătervātim, adv. [caterva], in companies, in troops, Lucr. 6, 1144; Verg. G. 3, 556; Sall. J. 97, 4; Liv. 23, 27, 5; 44, 41, 8; Col. 3, 19, 3; Plin. 10, 24, 35, § 72.