An enclave is a distinct geographical or geopolitical area which is wholly surrounded by that of another.[1]
An example of an enclave is the city of Cockrell Hill, Texas, which is completely surrounded by the city of Dallas.
It is possible for an enclave to also be an exclave (an area part of a larger one but separated by another geographical or geopolitical areas). An example of a dual enclave-exclave is the city of Glendale, Colorado: it is an enclave (as it is wholly surrounded by Denver), but since Denver is a consolidated city-county, it is an exclave of neighboring Arapahoe County.
Vatican City, San Marino (within Italy) and Lesotho (within South Africa) are the only completely enclaved countries.