(1):

(n.) A circular inclosure for the exhibition of feats of horsemanship, acrobatic displays, etc. Also, the company of performers, with their equipage.

(2):

(n.) A level oblong space surrounded on three sides by seats of wood, earth, or stone, rising in tiers one above another, and divided lengthwise through the middle by a barrier around which the track or course was laid out. It was used for chariot races, games, and public shows.

(3):

(n.) Circuit; space; inclosure.