What is "halfpace"

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.

Note: This term and quarterpace are rare or unknown in the United States, platform or landing being used instead.

n. (context archaic architecture English) A platform of a staircase where the stair turns back in exactly the reverse direction of the lower flight.