Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* grassātūra, ae, f. [grassor], a rioting, waylaying: in primis tuendae pacis a grassaturis et latrociniis seditionumque licentia curam habuit, Suet. Tib. 37; Dig. 48, 19, 16, § 6.