Definition from Wiktionary, the free dictionary
superstructure (plural superstructures)
- (nautical) Any structure built above the top full deck. (FM 55-501).
- Any material structure or edifice built on something else; that which is raised on a foundation or basis
- all that part of a building above the basement. Also used figuratively.
- (UK) (railroad) The sleepers, and fastenings, in distinction from the roadbed.
nautical: structure above deck