The headword adjective is in the epic/Ionic dialect, and probably quoted from Homer, Iliad 6.133 (itself quoted by Strabo 15.1.7). See also Aristophanes, Frogs 215, where Dover comments as follows: 'Nysa, a mountain associated with Dionysos and in particular with his birth (e.g. E. Ba. 556f), did not have an agreed location in the real world; Il. 6.133 puts [it] in Thrace, but Nysa in hBacch. (1) 8f is in the Middle East.'.
NF: There are many different site identifications, most commonly Thrake and India. However, Hesychius, besides giving the same entry as the Suda, has another 'Nysa and Nyseion' (nu742) which lists the following locations: Arabia, Ethiopia, Egypt, Babylon, Erythra(ian Sea), Thrake, Thessaly, Kilikia, India, Libya, Lydia, Makedonia, Naxos, around Pangaios, Syria.