orchestra

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A large group of musicians who play together on various instruments, usually including strings, woodwinds, brass instruments, and percussion instruments.
• noun The instruments played by such a group.
• noun The area in a theater or concert hall where the musicians sit, immediately in front of and below the stage.
• noun The front section of seats nearest the stage in a theater.
• noun The entire main floor of a theater.
• noun A semicircular space in front of the stage used by the chorus in ancient Greek theaters.

from The Century Dictionary.

• noun The part of a theater or other public place appropriated to the musicians.
• noun In modern music, a company of performers on such instruments as are used in concerted music; a band. ; ;
• noun In the early New England churches, the choir-gallery at the end opposite the pulpit: so called because in it were stationed the instrumentalists by whom the singing was accompanied.

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

• noun The space in a theater between the stage and the audience; -- originally appropriated by the Greeks to the chorus and its evolutions, afterward by the Romans to persons of distinction, and by the moderns to a band of instrumental musicians. Now commonly called orchestra pit, to distinguish it from the section of the main floor occupied by spectators.
• noun The space in the main floor of a theater in which the audience sits; also, the forward spectator section of the main floor, in distinction from the parterre, which is the rear section of the main floor.
• noun The place in any public hall appropriated to a band of instrumental musicians.
• noun Loosely: A band of instrumental musicians performing in a theater, concert hall, or other place of public amusement.
• noun Strictly: A band suitable for the performance of symphonies, overtures, etc., as well as for the accompaniment of operas, oratorios, cantatas, masses, and the like, or of vocal and instrumental solos.
• noun A band composed, for the largest part, of players of the various viol instruments, many of each kind, together with a proper complement of wind instruments of wood and brass; -- as distinguished from a military or street band of players on wind instruments, and from an assemblage of solo players for the rendering of concerted pieces, such as septets, octets, and the like.
• noun (Mus.) The instruments employed by a full band, collectively.

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

• noun music A large group of musicians who play together on various instruments, usually including some from strings, woodwind, brass and/or percussion; the instruments played by such a group.
• noun A semicircular space in front of the stage used by the chorus in Ancient Greek and Hellenistic theatres.
• noun The area in a theatre or concert hall where the musicians sit, immediately in front of and below the stage, sometimes (also) used by other performers.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun seating on the main floor in a theater
• noun a musical organization consisting of a group of instrumentalists including string players