Definition of orchestra noun from the Oxford Advanced Learner's Dictionary

orchestra

noun
ˈɔːkɪstrə
 
; ˈɔːrkɪstrə
 
 
1 [countable + singular or plural verb] a large group of people who play various musical instruments together, led by a conductorShe plays the flute in the school orchestra.the Scottish Symphony OrchestraThe competition gave the young composer her first opportunity to write for a full orchestra. see also chamber orchestra, symphony orchestra2 the orchestra [singular] (North American English) (British English the orchestra stalls, the stalls) the seats that are nearest to the stage in a theatre