This entry is from Lexicon Ambrosianum (Ambrosianus B 12 sup. 45 and Laurentianus 59,16 fol. 187r) and its origin is in a scholion to Homer, Iliad 4.1: “and the gods, seated near Zeus, discussed in assembly”.
The headword verb is an epic form of the imperfect of ἀγοραόμαι which occurs not only in Homer but also in several post-classical epic poets (Apollonius of Rhodes, Quintus, Nonnus) who take Homer as their model. This same form is to be found also in Herodotus.
There is no agreement on the meaning of the verb in the Homeric passage because of its double use: to meet (intransitive) in assembly, and to speak in assembly. See e.g. Porphyrius, Questionum Homericarum ad Iliadem pertinentium reliquiae 4.1: “Aristarchus considered ἠγορόωντο as meaning they gathered together, but is better to say they discussed… If indeed [Homer] meant they gathered together, would have written οἱ δὲ θεοι πὰρ Ζηνὶ καθήμενοι ἠγερέθεντο ; and the gods, seated near Zeus, ἠγερέθεντο [gathered together]” (as in Iliad 11.770, 24.790 and elsewhere).