1. A nation whose boundaries are completely (or almost completely) surrounded by another nation.
2. In the Fallout series of games, the continuation of the United States government following the Nuclear Apocalypse of 2077. Despite the state of the world, the Enclave continued to make scientific breakthroughs in the fields of medicine and military weapons. The covert government's goals were to purge the Earth of any radiation induced mutations and restore America to it's former glory.
1. Vatican City in Italy.
2.Though the other factions scavenge weapons and armor from the Pre-War era, the Enclave has dedicated facilities to research, develop, and manufacture advanced energy weapons and power armor.