The headword adjective, here in the neuter nominative/accusative singular, is attested only in the sense of "unknowing" (cf. alpha 677, alpha 678). Adler reports that the Ambrosian Lexicon has this gloss for the headword a)i+dno/n, in which the root *wid- seems to have the sense "seen." But "unseen, obscure" is still not quite the same as "able to be seen through."