The Collaborative International Dictionary of English v.0.48:

Covered \Cov"ered\ (k?v"?rd), a.
   Under cover; screened; sheltered; not exposed; hidden.
   [1913 Webster]

   Covered way (Fort.), a corridor or banquette along the top
      of the counterscarp and covered by an embankment whose
      slope forms the glacis. It gives the garrison an open line
      of communication around the works, and a standing place
      beyond the ditch. See Illust. of Ravelin.
      [1913 Webster]