xyst

from The Century Dictionary.

• noun In ancient architecture, a covered portico or open court, of great length in proportion to its width, in which athletes performed their exercises; or, in Roman villas, sometimes, a garden walk planted with trees. Also xystos, xystus.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anc. Arch.) A long and open portico, for athletic exercises, as wrestling, running, etc., for use in winter or in stormy weather.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A xystus.