undefined
Americanadjective
-
without fixed limits; indefinite in form, extent, or application.
undefined authority; undefined feelings of sadness.
-
not given meaning or significance, as by a definition; not defined or explained.
an undefined term.
-
Mathematics. having no assigned or determinable value under particular conditions.
Any number divided by zero is undefined.
adjective
Other Word Forms
Etymology
Origin of undefined
First recorded in 1605–15; un- 1 + define ( def. ) + -ed 2 ( def. )
Explanation
If something is undefined it's not clear, such as your undefined vacation plans. You know you want to go somewhere during the third week of August, but you just don't know where. You can tell just by looking at it that undefined means "not defined." But you might be surprised that the root define comes from the Old French word defenir, meaning "to end, terminate, determine." In this case, define carries the meaning of "determine," but in a sense "end" and "terminate" apply as well. When you define something, that's the end of it — no more wondering. So if something is undefined, it's not yet determined.
Vocabulary lists containing undefined
Fish in a Tree
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
UCPS 6th Grade Roots List #3
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Means to an End: Fin
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The overall target is undefined, but it is pretty clear Champions League qualification will be a significant part of it.
From BBC ● Oct. 5, 2026
Unlike the nuclear sphere, where rules have been broadly understood since the Cold War, hybrid warfare escalation is "largely undefined", he said.
From Barron's ● Sep. 3, 2026
“This is absolutely the wrong solution to an undefined problem,” Ryan said.
From Los Angeles Times ● Jul. 14, 2026
The bulk of that comes from undefined enterprise applications, which SpaceX said will contribute to $22.7 trillion of the TAM.
From MarketWatch ● Jun. 10, 2026
A First Lady’s power is a curious thing—as soft and undefined as the role itself.
From "Becoming" by Michelle Obama
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
