Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sub -dŭbĭto, āre, v. n., to be a little doubtful or undecided, to have some hesitation (Ciceron.): antea subdubitabam, Cic. Att. 14, 15, 2: significabant tuae litterae, te subdubitare, quā essem erga illum voluntate, id. Fam. 2, 13, 2.