elephant door
n.— «Although the Civic Center has what the entertainment industry calls an “elephant door”—an extremely large opening that would be big enough to accommodate elephants from the days of circuses—the ride was just a few inches too tall.» —“Facing one crisis at a time” by Genevieve Diesing Journal Star (Peoria, Illinois) July 22, 2007. (source: Double-Tongued Dictionary)