Definition of "Alcatraz"

Ellipsis of Alcatraz Island.. An island in San Francisco Bay, Pacific Ocean, of California, United States, formerly the site of a famous prison  examples

Ellipsis of Alcatraz Federal Penitentiary., a famous former U.S. federal prison, on the island.  examples

Ellipsis of Fort Alcatraz., a U.S. coastal defense fort, predecessor of the prison.  examples