A villa was a type of house.
In the 22nd century, there were villas built into the cliffs of Suraya Bay, on Risa. In 2152, Captain Jonathan Archer contemplated spending his vacation on this planet in one of these villas, reading a few good books and, maybe, some diving in the bay. (ENT: "Desert Crossing")
Keyla remarked that all of the villas looked similar to one another, an excuse for her winding up in Archer's villa instead of her own. He noted that she had to "notice the subtle differences," and she gave the example of "the numbers on the doors." (ENT: "Two Days and Two Nights")