Thunder Bay
noun
a port in W Ontario, in S Canada, on Lake Superior: created in 1970 by the merger of twin cities (Fort William and Port Arthur) and two adjoining townships.
Also called
Lakehead.
British Dictionary definitions for thunder bay
Thunder Bay
noun
a port in central Canada, in Ontario on Lake Superior: formed in 1970 by the amalgamation of Fort William and Port Arthur; the head of the St Lawrence Seaway for Canada. Pop: 103 215 (2001)