From Longman Dictionary of Contemporary Englishenvelopeen‧ve‧lope /ˈenvələʊp $ -loʊp/ ●●● S3 noun [countable] 1 
TCMa thin paper cover in which you put and send a letter envelopes and stamps She tore open the envelope and frantically read the letter. He got a job stuffing envelopes (=filling them with letters) at the campaign headquarters. → sae, SASE2 COVERa layer of something that surrounds something elseenvelope of an envelope of gases around the planet3 → push the envelopeCOLLOCATIONSverbsopen an envelopeI opened the envelope, pulled out the document and read it.tear/rip open an envelope (=open it quickly and roughly)My fingers trembled as I tore open the envelope.slit open an envelope (=open it by cutting it)I quickly slit open the envelope.seal an envelope (=close it)She sealed the envelope and stuck on a stamp.stuff envelopes (=to put letters or documents into many envelopes, for example as part of a political campaign)We need volunteers to stuff envelopes and deliver leaflets.adjectivesa pre-paid/stamped-addressed envelope (=with a stamp/a stamp and an address already on it)A copy of the rules can be obtained by sending a stamped-addressed envelope to the above address.a self-addressed envelope (=one with your own name and address on)Enclose a self-addressed envelope with your application form.a brown/white etc envelopeThere was a large brown envelope on his desk.a manila envelope (=made from strong brown paper)a sealed envelope (=one that is firmly closed)The contract was delivered by special messenger in a sealed envelope.phraseson the back of an envelope (=used to describe a calculation or plan that is written down quickly on any available small piece of paper)She scribbled a few ideas on the back of an envelope.
TCMa thin paper cover in which you put and send a letter envelopes and stamps She tore open the envelope and frantically read the letter. He got a job stuffing envelopes (=filling them with letters) at the campaign headquarters. → sae, SASE2 COVERa layer of something that surrounds something elseenvelope of an envelope of gases around the planet3 → push the envelopeCOLLOCATIONSverbsopen an envelopeI opened the envelope, pulled out the document and read it.tear/rip open an envelope (=open it quickly and roughly)My fingers trembled as I tore open the envelope.slit open an envelope (=open it by cutting it)I quickly slit open the envelope.seal an envelope (=close it)She sealed the envelope and stuck on a stamp.stuff envelopes (=to put letters or documents into many envelopes, for example as part of a political campaign)We need volunteers to stuff envelopes and deliver leaflets.adjectivesa pre-paid/stamped-addressed envelope (=with a stamp/a stamp and an address already on it)A copy of the rules can be obtained by sending a stamped-addressed envelope to the above address.a self-addressed envelope (=one with your own name and address on)Enclose a self-addressed envelope with your application form.a brown/white etc envelopeThere was a large brown envelope on his desk.a manila envelope (=made from strong brown paper)a sealed envelope (=one that is firmly closed)The contract was delivered by special messenger in a sealed envelope.phraseson the back of an envelope (=used to describe a calculation or plan that is written down quickly on any available small piece of paper)She scribbled a few ideas on the back of an envelope. Examples from the Corpus
envelope• That night at the meeting, Karen had a big brown envelope in her bag.• The solution is also obvious - please check envelopes are not too tightly packed, if in doubt use a bigger envelope!• Entries must be on the back of a postcard or envelope no bigger than 5in × 6in. 2.• The small jet wallowed in the sky, on the edge of the envelope of control.• With trembling hands Mr Utterson opened the envelope.• Cornelius sat himself down and regarded the envelopes with suspicion.stuffing envelopes• Rae started by stuffing envelopes and in a year was directing the volunteers herself.• She also worked in abortion clinics stuffing envelopes or providing counseling over the phone.• She doesn't think that stuffing envelopes for the Democrats once every four years makes her an activist.envelope of• A bluish envelope of flame surrounds the particle as it burns.From Longman Business Dictionaryenvelopeen‧ve‧lope /ˈenvələʊp-loʊp/ noun [countable] a thin paper cover in which you put a letter → padded envelope → self addressed envelope → self addressed stamped envelope → stamped addressed envelopeOrigin envelope (1700-1800) French enveloppe, from Old French envoloper; → ENVELOP 