An endorheic basin is a closed drainage basin that has no outflow to the sea or ocean. It is a term used to describe a body of water that is surrounded by highlands or mountains that prevent water from leaving the area. Synonyms for the term endorheic basin can include closed basin, landlocked basin, internal drainage area, or isolated drainage basin. These terms are often used interchangeably in geography and hydrology textbooks, and they refer to the same concept of a geographic area with no outflow to the ocean. The term endorheic basin can also be used to describe a lake or a depression that is surrounded by higher terrain and has no visible outlet.