Synonyms for Lobby (same or very similar meaning)
WordNet sense 1 (a group of people who try actively to influence legislation):
pressure group, third house
WordNet sense 2 (a large entrance or reception room or area):
antechamber, anteroom, foyer, hall, vestibule, entrance hall
WordNet sense 3 (detain in conversation by or as if by holding on to the outer garments of; as for political or economic favors):
buttonhole
From the ODE community, based on WordNet
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