- a thing that envelops; wrapper; covering
- a folded paper container as for a letter, usually with a gummed flap for sealing
- the outer covering of a rigid airship
- the bag that contains the gas in a balloon or nonrigid airship
- the set of limitations, as for a particular aircraft, system, etc., within the boundaries of which it can operate safely and efficiently
- a set of limits or boundaries: usually in the informal phrase push the envelope, to go beyond or attempt to go beyond established rules, limits, expectations, etc.
- Astron. a cloudy mass surrounding the nucleus of a comet; coma
- Biol. any enclosing membrane, skin, shell, etc.
- Math. a curve that is tangent to every one of a family of curves, or a surface that is tangent to every one of a family of surfaces
Origin of envelopeFrench and Old French enveloppe from Old French envoluper: see envelop