the GNU version of the Collaborative International Dictionary of English
n. A long and open portico, for athletic exercises, as wrestling, running, etc., for use in winter or in stormy weather.
The Century Dictionary and Cyclopedia
n. 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.
Word Usage
"If you've never heard of an ancient portico whose name is pronounced ZIST, the spelling xyst may well elude you."