Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
abnūtīvus, a, um [abnuo], = negativus; hence subst.: abnūtīvum, i, n., a denying, refusal, Dig. 45, 1, 83; cf. Abnutivum: ἀπωμοτικόν, Gloss.