Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. annīsus (adn-), a, um, Part. of annitor
* 2. annīsus (adn-), ūs, m. [annitor], a striving, exertion: ut alieno adjuventur adnisu, Symm. Ep. 5, 74.