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Webster 1913 Edition
Halfpace
Half′paceˊ
(-pāsˊ)
, Noun.
 (Arch.) 
A platform of a staircase where the stair turns back in exactly the reverse direction of the lower flight. See 
Quarterpace
. ☞ This term and 
quarterpace 
are rare or unknown in the United States, platform 
or landing 
being used instead.