A deep pool in which the water often appears blue; (in later use) specifically a deep water-filled cylindrical hollow or cave in limestone, typically in a coastal area of the tropics.
Origin
Mid 19th century.
Definition of blue hole in US English:
blue hole
noun
Jamaican
A deep pool in which the water often appears blue; (in later use) specifically a deep water-filled cylindrical hollow or cave in limestone, typically in a coastal area of the tropics.