Definition of "orchestra"

orchestra

/ˈɔɹkəstɹə/

noun
plural orchestras or (rare) orchestrae
1. (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.
  Quotations
  It requires quite an orchestra to get a train to start; the guard blows his horn, the stationmaster rings a large bell, and the engine whistles.
  1941 February, Voyageur, “The Railways of Greece”, in Railway Magazine, page 67
  Musicians play their instruments. I play the orchestra.
  2015, Aaron Sorkin, Walter Isaacson, Steve Jobs, spoken by Steve Jobs (Michael Fassbender)
2. A semicircular space in front of the stage used by the chorus in Ancient Greek and Hellenistic theatres.
3. 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.