envelope

SayEN-vuh-lohp/ˈɛnvəˌloʊp//ˈɛnvələʊp/

13 meanings of envelope

1
nouncountable
A flat paper cover that holds a letter or card for mailing.
Like a small paper pocket that keeps a letter safe in the mail.
She sealed the envelope and added a stamp before mailing it.
He tore open the envelope to read the birthday card inside.
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2
nouncountable
A covering or layer that wraps around something.
Like a blanket wrapped tightly around something.
A thick envelope of fog hid the whole valley from view.
Each seed rests inside a soft envelope of pulp.
Similarwrapper
3
nouncountable
The safe limits that a machine or system must stay inside to work well.
Like the lines on a road that show how fast and how far you can safely drive.
Test pilots push each aircraft to the edge of its envelope.
The new engine stays inside a safe envelope even at high speed.
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4
nouncountable
A covering layer, such as a membrane, that surrounds part of a cell.
Like the skin of a grape that holds everything inside.
A virus often carries a protective envelope made of fatty material.
The cell's nucleus sits inside a thin envelope.
Similarmembrane
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5
nouncountable
The large fabric bag that holds the gas which lifts a balloon or airship.
Like a big cloth bag that traps air to keep something floating.
The balloon's envelope filled slowly with hot air.
Crew members inspected the envelope for tears before launch.
Similargasbag
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6
nouncountable
The way a sound's loudness changes over time, from start to finish.
Like how a clap is loud right away but a slow whistle grows little by little.
She adjusted the envelope to make the note fade out slowly.
A sharp envelope gives the drum its punchy sound.
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7
nouncountable
The address details sent with a message to help it reach the right place, kept apart from the message itself.
Like the address on the outside of a letter that the mail carrier reads, not the note inside.
The mail server reads the envelope to learn where to send the message.
Routing details live in the envelope, not in the message you read.
Similarheader
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8
nouncountable
A curve or surface that just touches every curve in a related group.
Like a curved fence that just touches the edge of every circle inside it.
The teacher drew an envelope that touched every line in the family.
Each circle in the set just touches the envelope at one point.
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9
nouncountable
A smooth curve that outlines the peaks of a changing signal.
Like a line drawn along the tops of the waves in the sea.
The radio detects the envelope of the wave to recover the sound.
Engineers traced the envelope along the tops of the signal's peaks.
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10
nouncountable
A faint, cloudy layer surrounding the head of a comet.
Like the fuzzy glow around a streetlight on a foggy night.
Through the telescope, a soft envelope glowed around the comet.
The comet's envelope grew brighter as it neared the sun.
Similarcoma
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11
nouncountable
A low bank of earth built as a defense, sometimes inside a ditch and sometimes beyond it.
Like a low wall of dirt built to hide behind during a fight.
Soldiers crouched behind the envelope to avoid enemy fire.
The fort's envelope blocked a clear shot at the inner wall.
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Less common meanings

12
verbraretransitive
To put something inside a paper cover for mailing.
Like slipping a card into a paper pocket before sending it.
Please envelope these tickets before you mail them.
I suspect you write letters as hens lay eggs, find that Lady Hamilton finds them, envelopes them, puts them before you as official letters, and you direct them as per memorandum affixed.
1857, Augustus de Morgan, “[Correspondence between Sir William Rowan Hamilton and Professor Augustus De Morgan.] From A. De Morgan to Sir…Here, envelopes means puts the letters inside envelopes.
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13
Sayen-VEL-uhp/ɛnˈvɛləp/
verbarchaic
Archaic form of envelop. An old spelling meaning to wrap or surround something completely.
Again, if the plane of the impressed couple intersects the mean plane between N and C, it will envelope the cone whose focals are ON, ON′, and whose internal axis is therefore OA.
1877, James Booth, A Treatise on Some New Geometrical MethodsHere, envelope means wrap around or surround completely.
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Practice

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Origin

It comes from the French word "enveloppe."