A territory entirely surrounded by another country's territory. Used in legal and geographical contexts.
Vatican City is an enclave within Italy.
exclave
A part of a country separated from the main territory and surrounded by foreign land. Often contrasted with 飛び地 (とびち), a more common term for exclave.
Kaliningrad is a Russian exclave.
包領 specifically means an enclave (territory surrounded by another country), whereas 飛び領土 can refer to either an enclave or an exclave depending on context.
Compound of 飛び (とび, 'jumping' or 'detached') and 領土 (りょうど, 'territory'). The term is a modern legal coinage, likely influenced by the concept of 飛び地 (とびち).