envelope

Meanings

1. 1
   noun

   A flat paper cover in which you put a letter before posting it.

   She sealed the letter in an envelope and wrote the address on the front.

2. 2
   verb

   To put something inside an envelope.

   He carefully enveloped the cheque before mailing it.

3. 3
   noun

   The limit of what a system, especially an aircraft, can safely do.

   Test pilots are trained to push the envelope of a new aircraft.

PIE word *h₁én From French enveloppe. The engineering sense is derived from flight envelope. The verb is from the noun.

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