amphitheater

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An oval or round structure having tiers of seats rising gradually outward from a central open space or arena.
2. n. An arena where contests and spectacles are held.
3. n. A level area surrounded by upward sloping ground.
4. n. An upper, sloping gallery with seats for spectators, as in a theater or operating room.

Century Dictionary and Cyclopedia

1. n. In anc. Rom. arch., an edifice devoted to the exhibition of gladiatorial contests and the combats of wild beasts. Such edifices were elliptical in form, and consisted of a central area or arena, surrounded by a wall, from which, sloping upward and outward, were rows of seats for the spectators. The earliest amphitheaters were made of wood; the first built of stone date from the time of Augustus. The Colosseum or Flavian amphitheater at Rome was the largest of all the ancient amphitheaters, being capable of containing from 80,000 to 90,000 persons. Those at Nimes and Verona are among the best examples remaining. The dimensions of the latter are 505½ by 403 feet, with a height of 100 feet.
2. n. Anything resembling an amphitheater in form, as an oval or circular building with seats rising behind and above each other around a central open space, or a natural area surrounded by rising ground; in horticulture, a sloping arrangement of shrubs and trees.
3. n. The uppermost gallery of a modern theater.

Wiktionary

1. n. US A semi-circular acoustic backdrop behind performers for an outdoor venue.
2. n. historical A completely circular outdoor arena; a classic European amphitheatre.

GNU Webster's 1913

1. n. An oval or circular building with rising tiers of seats about an open space called the arena.
2. n. Anything resembling an amphitheater in form; as, a level surrounded by rising slopes or hills, or a rising gallery in a theater.

WordNet 3.0

1. n. an oval large stadium with tiers of seats; an arena in which contests and spectacles are held
2. n. a sloping gallery with seats for spectators (as in an operating room or theater)