The second vowel of this headword is properly omega, as here. LSJ register a variant labro/nion in Hesychius [lambda25], but in fact Latte there makes the correction.
[1] More fully in Photius, Lexicon lambda9 Theodoridis: 'a kind of cup, wide in its structure, and having big "ears" (sc. handles).' He names Menander but does not quote a passage. See in fact line 4 of fr. 24 Koerte, now 26 K.-A., and labrw/nioi in fr. 437 Koerte, now 395 K.-A. Neither passage gives any indication of the physical form of the object, though in each instance it occurs in a list of drinking vessels. One imagines something like a phiale (phi 283, phi 284) but with handles.
[2] (Addendum lacking in ms. A.) Likewise in Theognostus, Canones 298.6. Besides this masculine and the neuter, a feminine labrwni/a is also noted in Eustathius' Commentary on the Iliad.