Envelope

noun

'ɛnvə,loʊp

Noun

a natural covering (as by a fluid)
“the spacecraft detected an envelope of gas around the comet”
Type of:CoverCovering
the maximum operating capability of a system (especially an aircraft)
“test pilots try to push the envelope”
the bag containing the gas in a balloon
Similar:Gasbag
Type of:Bag
a curve that is tangent to each of a family of curves
Type of:Curve
a flat (usually rectangular) container for a letter, thin package, etc.
Type of:Container
any wrapper or covering
Type of:WrappingWrapWrapper