Fuca, Or Juan De Fuca, Strait of, a body of water lying between the N. W. portion of Washington territory and the S. E. extremity of Vancouver island. It enters the Pacific at Cape Flattery, and communicates with the gulf of Georgia through Rosario and Haro straits. It is about 80 m. long, 11 m. wide at its W. and 25 m. at its E. end, and free from shoals.