Definition of superfortress in English:

superfortress

noun

  • 1A very large and heavily defended fortress.

  • 2A bomber aeroplane larger and more technically advanced than the Boeing B-17 ‘flying fortress’; specifically (an informal name for) the Boeing B-29 long-range heavy bomber aeroplane developed in the early 1940s.

Origin

Early 20th century; earliest use found in The Manchester Guardian.