Hesychius glosses this headword as ὑμνοῦσιν (for which verb see e.g. upsilon 112, upsilon 115). Very rarely found, and not before the Hellenistic poets, it is evidently quoted from somewhere, most probably Callimachus (Hecale fr. 372); but see also Nicander, Alexipharmaca 525.
For the verb (and first gloss) see also upsilon 42.