1
: fully developed and mature : grown-up
an adult lion
2
: of, relating to, intended for, or befitting adults
an adult approach to a problem
3
: dealing in or with explicitly sexual material
adult bookstores
adult movies
: one that is adult
especially
: a human being after an age (such as 21) specified by law
adulted; adulting; adults
1
informal
: to behave like an adult : to attend to the ordinary tasks required of a responsible adult
Do we really have to adult today?—
Lauren Merola
Lauren MerolaStop complaining that you have to adult today. Being an adult is awesome.—Suzanne Lucas
Suzanne LucasLearning how to "adult" is a necessity for these college freshmen in order to figure out new medication schedules and if their parents' insurance will cover impromptu ER visits.—Meredith Newman
Meredith Newman2
informal
: to become an adult
It could be something small, like bailing on your friends at the last second. Or something bigger, like not showing up for work. Whatever the case may be, it's a sign you haven't fully "adulted" if you constantly slack off on your responsibilities.—Carolyn Steber
Carolyn SteberBut there is one real benefit to growing older and adulting: We essentially get to do whatever we want to do.—Sharon Pope
Sharon PopeSynonyms
Examples of adult in a Sentence
Adjective
preparing children for adult life
We need to approach this in an adult way.
Noun
Her books appeal both to children and to adults.
Children must be accompanied by an adult in the museum.
Only adults can purchase alcohol.
This film is for adults only. Minors are not admitted.
People who are close friends as children aren't always friends as adults.
studying interactions between young birds and adults
Recent Examples on the Web
Henry A. Kissinger, Foreign Affairs, 1 Mar. 2012
At first, the dynamic seems ambiguous: closer to that between a mom and her barely adult son than a wife and her husband.
—Michael O'Sullivan, Washington Post, 15 Nov. 2023
Karen Weintraub, USA TODAY, 13 Dec. 2024
Donations of new or gently used coats, hats, scarves, gloves and boots for adults and children age one month to 11 years old are being sought, a news release said.
—Mike Danahey, Chicago Tribune, 13 Dec. 2024
Rowan Jacobsen, Scientific American, 1 Feb. 2024
Hummels compares these definitions to stages or transitions in life: child to adult to senior citizen.
—Avery Hurt, Discover Magazine, 12 Feb. 2024
See all Example Sentences for adult 
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Adjective
The next decades will witness, for the first time, the full impact of one-child families on adult Chinese society.
—Henry A. Kissinger, Foreign Affairs, 1 Mar. 2012
At first, the dynamic seems ambiguous: closer to that between a mom and her barely adult son than a wife and her husband.
—Michael O'Sullivan, Washington Post, 15 Nov. 2023
Noun
From 2011 to 2019, incidence of colon cancer fell by about 1% annually, mainly among older adults.
—Karen Weintraub, USA TODAY, 13 Dec. 2024
Donations of new or gently used coats, hats, scarves, gloves and boots for adults and children age one month to 11 years old are being sought, a news release said.
—Mike Danahey, Chicago Tribune, 13 Dec. 2024
Verb
For more confirmation that bioelectricity could control body shape and growth, Levin turned to African clawed frogs, common lab animals that quickly metamorphose from egg to tadpole to adult.
—Rowan Jacobsen, Scientific American, 1 Feb. 2024
Hummels compares these definitions to stages or transitions in life: child to adult to senior citizen.
—Avery Hurt, Discover Magazine, 12 Feb. 2024
See all Example Sentences for adult
Dictionary Entries Near adult
Cite this Entry
“Adult.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/adult. Accessed 18 Dec. 2024.
Copy CitationKids Definition
1
: fully developed and mature
2
: of, relating to, or characteristic of adults
Etymology
Adjective
from Latin adultus "having grown up," from adolescere "to grow up" — related to adolescence
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