Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dē-sponso, no perf., ātum, 1, v. a., to betroth (post-Aug.), Suet. Caes. 1; id. Claud. 27; Aur. Vict. Orig. 13: viro justo, Ambros. in Luc. 10, 21; Vulg. Matt. 1, 18.