plural extensions
1
: the act of extending something: such as
a
: the act of making something longer or greater
extension of the patient's life
He's asking for a contract extension.
b
: the act of straightening or stretching something (such as an arm or a leg)
He did some leg extensions. [=exercises in which you extend your legs]
Make sure that the muscles get the proper amount of extension.
2
: extra time allowed for doing something
I missed the deadline but was granted an extension.
3
: something (such as an interest or activity) that develops from something else
—+ of
Writing screenplays was a natural/logical extension of his career as a novelist and his longtime interest in film.
Note: The phrase by extension is used to say that what follows comes from or is connected with something that has already been mentioned.
4
a
: a part that is added on to something to make it larger or longer
They built an extension on their house.
a road extension
b
5
: an extra telephone that is connected to the main line
We've added another extension in our daughter's bedroom.
also
: a telephone number that connects to a particular extension
I dialed her extension, but she wasn't at her desk.
Extension 365, please.
Cite this Entry
“Extension.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/extension. Accessed 18 Jun. 2026.
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