Source : Webster's Revised Unabridged Dictionary (1913)

Anteroom \An"te*room\, n.
   A room before, or forming an entrance to, another; a waiting
   room.

Source : WordNet®

anteroom
     n : a large entrance or reception room or area [syn: {antechamber},
          {entrance hall}, {hall}, {foyer}, {lobby}, {vestibule}]