Definition of envelope
1
: a flat usually paper container (as for a letter)
3a
: the outer covering of an aerostat
b
: the bag containing the gas in a balloon or airship
4a
: a natural enclosing covering (such as a membrane, shell, or integument)
b
: a lipoprotein unit membrane that forms the outer layer of some virions
5a
: a curve tangent to each of a family of curves
b
: a surface tangent to each of a family of surfaces
6
: a set of performance limits (as of an aircraft) that may not be safely exceeded
also
: the set of operating parameters that exists within these limits
7
: a conventionally accepted limit
new computers that push the envelope
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Who Knew?
-
- What is a ruelle?

Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
Spell words. Make bears.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Words at Play
Ask the Editors
The first known use of envelope was circa 1714
See more words from the same year