envelope meaning and definition

ENVELOPE noun

Definition of envelope (noun)

1. a flat (usually rectangular) container for a letter, thin package, etc.
2. any wrapper or covering
3. a curve that is tangent to each of a family of curves
4. a natural covering (as by a fluid)
   • "the spacecraft detected an envelope of gas around the comet"
5. the maximum operating capability of a system (especially an aircraft)
   • "test pilots try to push the envelope"
6. the bag containing the gas in a balloon
   • synonyms: gasbag