Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
comprĕcātĭo, ōnis, f. [comprecor], a common or public imploring of a deity: sollennis deorum, Liv. 39, 15, 2; plur.: deūm inmortalium, Gell. 13, 22, 1.