envelope

American  

[en-vuh-lohp, ahn-] / ˈɛn vəˌloʊp, ˈɑn- /

noun

1. a flat paper container, as for a letter or thin package, usually having a gummed flap or other means of closure.

2. something that envelops; a wrapper, integument, or surrounding cover.

3. Biology.  a surrounding or enclosing structure, as a corolla or an outer membrane.

4. Geometry.  a curve or surface tangent to each member of a set of curves or surfaces.

5. Radio.  (of a modulated carrier wave) a curve connecting the peaks of a graph of the instantaneous value of the electric or magnetic component of the carrier wave as a function of time.

6. the fabric structure enclosing the gasbag of an aerostat.

7. the gasbag itself.

8. Electronics.  the airtight glass or metal housing of a vacuum tube.

9. the technical limits within which an aircraft or electronic system may be safely operated.

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idioms

1. push the envelope,  to stretch established limits, as in technological advance or social innovation.

envelope British  

/ ˈɒn-, ˈɛnvəˌləʊp /

noun

1. a flat covering of paper, usually rectangular in shape and with a flap that can be folded over and sealed, used to enclose a letter, etc

2. any covering or wrapper

3. biology any enclosing structure, such as a membrane, shell, or skin

4. the bag enclosing the gas in a balloon

5. maths a curve or surface that is tangent to each one of a group of curves or surfaces

6. electronics the sealed glass or metal housing of a valve, electric light, etc

7. telecomm the outer shape of a modulated wave, formed by the peaks of successive cycles of the carrier wave

8. informal  to push the boundaries of what is possible

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Etymology

Origin of envelope

1700–10; < French enveloppe, derivative of envelopper to envelop

Example Sentences

The active galactic nucleus heats the surrounding gas envelope in a way that resembles how fusion heats the outer layers of a star, producing a similar outward appearance.

From Science Daily

Even so, the kaleidoscope of tales and vignettes, and the blurring of the banal with the macabre, produces a dusky, dreamlike atmosphere that envelopes one’s thoughts like a fine mist.

From The Wall Street Journal

That is why delivering the good news was long left to trustees or lawyers, or in envelopes with details of how to access cash.

From The Wall Street Journal

Ackman himself has a history of pushing the envelope with novel investment ideas and endeavors, not all of which go according to plan.

From The Wall Street Journal

He gave one an envelope of cash he’d saved and told her to take herself to Disneyland.

From Los Angeles Times

Related Words

• bag
• box
• casing
• coat
• container
• jacket
• pocket
• pouch