Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĭnobservantĭa, ae, f. [inobservans], inattention, negligence, irregularity: quae ne fecisse inobservantia quadam videatur, Quint. 4, 2, 107; Suet. Aug. 76.