city & port in W Ontario, Canada, on Lake Superior: formed in 1970 by the merger of Fort William and Port Arthur: pop. 114,000
after the bay on which it is located: the bay was named for the thunderbird of Indian legend
See Thunder Bay in American Heritage Dictionary 4
A city of southwest Ontario, Canada, on Thunder Bay, an inlet on the northwest shore of Lake Superior. A major port and industrial center, it was created in 1970 by the amalgamation of the twin cities of Port Arthur and Fort William. Population: 109,000.