Definify.com
Webster 1913 Edition
Choir
Choir
,Noun.
 [OE. 
quer
, OF. cuer
, F. chœur
, fr. L. chorus 
a choral dance, chorus, choir, fr. Gr. [GREEK], orig. dancing place; prob. akin to [GREEK] inclosure, L. hortus 
garden, and E. yard
. See Chorus
.] 1. 
A band or organized company of singers, especially in church service. 
[Formerly written also 
quire
.] 2. 
That part of a church appropriated to the singers. 
3. 
(Arch.) 
The chancel. 
Choir organ 
(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. 
– Choir screen
, 
Choir wall 
(Arch.)
, a screen or low wall separating the choir from the aisles. 
– Choir service
, the service of singing performed by the choir. 
T. Warton.
Webster 1828 Edition
Choir
CHOIR
, n.1.
  A collection of singers, especially in divine service, in a church.2.
  Any collection of singers.3.
  That part of a church appropriated for the singers, separated from the chancel and the nave.  In congregational and some other churches, the singers are placed in certain seats in the galleries.4.
  In nunneries, a large hall adjoining to the body of the church, separated by a grate, where the nuns sing the office.