Comparable entry, according to Adler, in the Ambrosian Lexicon. The headword is an adjective -- here in the masculine accusative singular or neuter nominative/accusative singular; either way, presumably quoted from somewhere -- used primarily of drugs (e.g. for the pain resulting from flagellation) and once (in the Greek Anthology) of the god Paean.
A number of adjectives are formed from the root o)du/nh, physical or mental pain: cf. nu 530, pi 1232, pi 1989, upsilon 347; and cf. the English 'anodyne'.