Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prōpulsātĭo, ōnis, f. [propulso], a driving back, a keeping or warding off, a repelling, repulse (rare but class.): periculi, Cic. Sull. 1, 2: criminis, Tiro ap. Gell. 7, 3, 15.