halfpace

from The Collaborative International Dictionary of English v.0.48

Halfpace \Half"pace`\ (-p[=a]s`), n. (Arch.)
   A platform of a staircase where the stair turns back in
   exactly the reverse direction of the lower flight. See
   {Quarterpace}.
   [1913 Webster]

   Note: This term and {quarterpace} are rare or unknown in the
         United States, {platform} or {landing} being used
         instead.
         [1913 Webster]