definition
Americannoun
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the act of defining, or of making something definite, distinct, or clear.
We need a better definition of her responsibilities.
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the formal statement of the meaning or significance of a word, phrase, idiom, etc., as found in dictionaries. An online dictionary resource, such as Dictionary.com, can give users direct, immediate access to the definitions of a term, allowing them to compare definitions from various dictionaries and stay up to date with an ever-expanding vocabulary.
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the condition of being definite, distinct, or clearly outlined.
His biceps have great muscle definition.
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Optics. sharpness of the image formed by an optical system.
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Radio and Television. the accuracy of sound or picture reproduction.
noun
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a formal and concise statement of the meaning of a word, phrase, etc
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the act of defining a word, phrase, etc
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specification of the essential properties of something, or of the criteria which uniquely identify it
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the act of making clear or definite
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the state or condition of being clearly defined or definite
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a measure of the clarity of an optical, photographic, or television image as characterized by its sharpness and contrast
Other Word Forms
Derived Forms
Etymology
Origin of definition
First recorded in 1350–1400; Middle English diffinicioun, from Old French diffinition, from Latin dēfīnītiōn- (stem of dēfīnītiō ), equivalent to dēfīnīt(us) ( see definite) + -iōn- noun suffix ( see -ion)
Explanation
A good definition explains concisely what something means. Dictionaries include definitions, even for the word definition! A definition precisely explains the fundamental state or meaning of something, often given formally as by lexicographers writing a dictionary or legislators writing laws. It can also refer to a sharply detailed image or concept — like how clear the picture is on a high-definition TV or how cut a Calvin Klein model's abs are.
Vocabulary lists containing definition
Dictionary Words: Lexicography Lingo
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Language and Grammar - Introductory
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Academic Vocabulary: Core Tier 2 Words, List 2
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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.
IPOs by definition are stock events, but options trading will likely become the main event.
From Barron's • Jun. 10, 2026
If that were the case there would be no net effect on the global stock market from this World Cup effect, since by definition there always is the same number of winning and losing teams.
From MarketWatch • Jun. 9, 2026
"Repealing the defence would, by definition, make this kind of reasonable parental behaviour prosecutable."
From BBC • Jun. 7, 2026
A team led by Los Alamos scientist Roxana Bujack used geometry to build a mathematical definition of color perception based on hue, saturation, and lightness.
From Science Daily • Jun. 7, 2026
“Oh, well, I think that depends on your definition of ‘real.’
From "The Wrong Way Home" by Kate O’Shaughnessy
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.
