Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
assultus (ads-), ūs, m. [assilio], a leaping to or toward, an attack, assault: locum variis adsultibus urget, Verg. A. 5, 442: adsultibus et velocitate corporum uti, Tac. A. 2, 21.