blockhouse

noun, plural block·hous·es [blok-hou-ziz] /ˈblɒkˌhaʊ zɪz/.

1. Military. a fortified structure with ports or loopholes through which defenders may direct gunfire.
2. Also called garrison house. (formerly) a building, usually of hewn timber and with a projecting upper story, having loopholes for musketry.
3. a house built of squared logs.
4. Rocketry. a structure near a launching site for rockets, generally made of heavily reinforced concrete, for housing and protecting personnel, electronic controls, and auxiliary apparatus before and during launching operations.

noun

1. (formerly) a wooden fortification with ports or loopholes for defensive fire, observation, etc
2. a concrete structure strengthened to give protection against enemy fire, with apertures to allow defensive gunfire
3. a building constructed of logs or squared timber
4. a reinforced concrete building close to a rocket-launching site for protecting personnel and equipment during launching