What does the French word 'Detroit' mean?

Answer 1

The words 'Détroit' and 'Détroits' mean strait or straits. For a strait is a 'narrow navigable channel that connects two larger navigable bodies of water'. The term doesn't find its use just as the city in Michigan. For it also is the French way of saying the Dardanelles [le détroit des Dardanelles] off Turkey, the Straits of Gibraltar [le détroit de Gibraltar] near Spain, and the Straits of Magellan [le détroit de Magellan] off southernmost Argentina and Chile.
Strait.
'un détroit' is a narrow channel of water connecting two larger bodies of water (a strait or straits), like the 'détroit de Gibraltar' between Spain and North Africa.

Answer 2

In French, "détroit" means strait or narrow passage of water between two land masses. The city of Detroit in Michigan, USA, was named after the Detroit River, which connects Lake St. Clair and Lake Erie.