Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
indāgātĭo, ōnis, f. [1. indago], a searching into, investigation (class. but rare): initiorum, Cic. Tusc. 5, 24, 69: atque inventio veri, id. Off. 1, 5, 15: rarioris verbi, Gell. 18, 2, 6.