blockhouse

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A military fortification constructed of sturdy material, such as concrete, and designed with ports for defensive firing or observation.
2. n. A heavily reinforced building used for launch operations of missiles and space launch vehicles.
3. n. A fort made of squared timbers with a projecting upper story.

Century Dictionary and Cyclopedia

1. n. Originally, a detached fort blocking the access to a landing, a mountain pass, narrow channel, etc.; in later use, an edifice of one or more stories, constructed chiefly of hewn timber, and supplied with loopholes for musketry and sometimes with embrasures for cannon. When of more than one story, the upper is made to overhang the lower, and is furnished with machicolations or loopholes in the overhung floor, so that a lunging fire can be directed against the enemy in close attack. When a blockhouse stands alone, it constitutes an independent fort, a form which is often very useful in a rough country; when it is erected in the interior of a fieldwork, it becomes a retrenchment or redoubt. Stockades are sometimes called blockhouses.

Wiktionary

1. n. A sturdy military fortification, often of concrete, with gunports.
2. n. A reinforced building from which to control hazardous operations, such as an explosion or a rocket launch.
3. n. dated A temporary wooden fortification with a projecting upper story.

GNU Webster's 1913

1. n. (Mil.) An edifice or structure of heavy timbers or logs for military defense, having its sides loopholed for musketry, and often an upper story projecting over the lower, or so placed upon it as to have its sides make an angle wit the sides of the lower story, thus enabling the defenders to fire downward, and in all directions; -- formerly much used in America and Germany.
2. n. West. & South. U. S. A house of squared logs.

WordNet 3.0

1. n. a stronghold that is reinforced for protection from enemy fire; with apertures for defensive fire