1. (in an ancient Roman villa) a garden walk planted with trees.
2. (in ancient Greek and Roman architecture) a covered portico, as a promenade.
The ordinary length of a xyst was a stadium, and, as this bridge was at the southern end of the Xyst, the first wall which passed along the northern end of it must have been about 600 feet to the north of the bridge…
— , Archaeologia: Or Miscellaneous Tracts Relating to Antiquity: Volume 44 , 1873
Paganism never troubled itself to be angry with mere philosophers who aired their elegant doubts in the shady xystus.
— F.W. Farrar , “The Victories of Christianity,” The Witness of History to Christ , 1870
Xyst comes from the Greek xystós meaning “a covered colonnade,” a space that was used for athletic exercises in ancient Greece. It entered English in the mid-1600s.