Source : Webster's Revised Unabridged Dictionary (1913)

Circus \Cir"cus\, n.; pl. {Circuses}. [L. circus circle, ring,
   circus (in sense 1). See {Circle}, and cf. {Cirque}.]
   1. (Roman Antiq.) 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.

   Note: The Circus Maximus at Rome could contain more than
         100,000 spectators. --Harpers' Latin Dict.

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

   3. Circuit; space; inclosure. [R.]

            The narrow circus of my dungeon wall. --Byron.