Definitions of offstage:

• noun:   a stage area out of sight of the audience
• adjective:   situated or taking place in the area of a stage not visible to the audience

  Example: "Offstage noises"

• adjective:   withheld from public view or attention

  Example: "Offstage political meetings"

• adverb:   not in public

  Example: "The deal was done offstage"

• adverb:   behind the scenes; not on stage

  Example: "The actors were waiting offstage"