Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĭn-ŏpīnor, ātus sum, 1, v. dep., to suppose, think, opine: Alexander facilius inopinatus, Val. Res Gest. Alex. M. 1, 52 Mai. (but a false read. for opinor, Gell. 18, 7, 5).