choir

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

• noun An organized company of singers, especially one performing church music or singing in a church.
• noun The part of a church used by such a company of singers.
• noun The part of the chancel in a cruciform church that is occupied by this company of singers.
• noun A group of instruments of the same kind.
• noun A division of some pipe organs, containing pipes suitable for accompanying a choir.
• noun An organized group.
• noun One of the orders of angels.
• intransitive verb To sing in chorus.

from The Century Dictionary.

• To sing in company.
• noun All that part of a cruciform church which is beyond, eastward of or farther from the main entrance than the transept; the eastern arm of the cross: so named because the choir proper (see def. 3) is usually in that part of the church and occupies nearly all of it.
• noun A group of instruments of the same class or of related organ-stops, as a trombone choir, a diapason choir, etc.
• noun Any company of singers.
• noun An organized company of singers. Especially, such a company employed in church service.
• noun A choral society, especially one that performs sacred music. In eight-part music a chorus is divided into first and second choirs. In the Anglican Church, an official body consisting of the minor canons, the choral vicars, and the choristers connected with a cathedral, whose function is to perform the daily choral service. Such a choir is divided into two sections, called decani and cantoris, sitting on the right and left sides respectively; of these the decani side forms the leading or principal section. See cantoris, decani.
• noun That part of a church which is, or is considered as, appropriated for the use of the singers.
• noun A company; a band, originally of persons dancing to music: loosely applied to an assembly for any ceremonial purpose.
• noun Formerly and still occasionally quire.

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

• noun A band or organized company of singers, especially in church service.
• noun That part of a church appropriated to the singers.
• noun (Arch.) The chancel.
• noun (Mus.) one of the three or five distinct organs included in the full organ, each separable from the rest, but all controlled by one performer; a portion of the full organ, complete in itself, and more practicable for ordinary service and in the accompanying of the vocal choir.
• noun (Arch.) a screen or low wall separating the choir from the aisles.
• noun the service of singing performed by the choir.

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

• noun Singing group; group of people who sing together; company of people who are trained to sing together
• noun The part of a church where the choir assembles for song
• noun one of the nine ranks or orders of angels

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

• noun a family of similar musical instrument playing together
• noun a chorus that sings as part of a religious ceremony
• noun the area occupied by singers; the part of the chancel between sanctuary and nave
• verb sing in a choir