What does the word envelope mean?

Usage examples for envelope

  1. " No, sir; I was told not to open this envelope till I was fifty miles away from where it was given me. – The Young Musician or, Fighting His Way by Horatio Alger
  2. Perhaps we can get the information we want from the outside of the envelope." – The Mystery of 31 New Inn by R. Austin Freeman
  3. She tore open the envelope, and took out a letter. – The Man Who Knew by Edgar Wallace