From The Collaborative International Dictionary of English v.0.48 [gcide]:
Foyer \Foy`er"\, n. [F., fr. LL. focarium fireplace. See
Focus, n.]
1. A lobby in a theater; a greenroom.
[1913 Webster]
2. The crucible or basin in a furnace which receives the
molten metal. --Knight.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
foyer
n 1: a large entrance or reception room or area [syn:
anteroom, antechamber, entrance hall, hall,
foyer, lobby, vestibule]