Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĭmāgĭnātĭo, ōnis, f. [imaginor], a mental image, fancy, imagination (postAug.): libidinum imaginationes in somno, Plin. 20, 7, 26, § 68: provincias secretis imaginationibus agitans, Tac. A. 15, 36; Aug. Conf. 7, 5.