1. a monumental archway, often erected in permanent materials as a commemorative structure, straddling the line of march of a victorious army during a triumphal procession.
2. an architectural motif resembling in its composition an ancient Roman triumphal arch, having one high central archway flanked by side elements composed of lower arches, compartments, bas-reliefs, etc., the whole usually adorned by a huge order.
[ 1540-50 ]