1
: an abnormal benign or malignant new growth of tissue that possesses no physiological function and arises from uncontrolled usually rapid cellular proliferation
called also neoplasm
2
: a swollen or distended part
… houses that bulged with the tumors and warts of … ornamental architecture …—
W. A. White
W. A. WhiteExamples of tumor in a Sentence
the scan showed a small tumor in her abdomen
Recent Examples on the Web
The Bidens lost their son, Beau, to a brain tumor in 2015.
—Madeline Mitchell, USA Today, 22 May 2025
So when his young grandson develops a brain tumor, Joe needs a way to pay for the boy’s treatment and make amends for his own indifferent parenting.
—Jeannette Catsoulis, New York Times, 22 May 2025
For anyone unfamiliar, a tumor board is a multidisciplinary panel where specialists across the cancer continuum—medical oncologists, surgical oncologists, radiologists, pathologists, radiation oncologists, geneticists and sometimes ethicists—all come together to discuss complex patient cases.
—Sanjay Juneja, Forbes.com, 22 May 2025
The administration has responded to blowback from the children’s expulsions and those of other U.S. citizen minors, including a child with cancer and one recovering from a rare brain tumor, by saying the mothers were in the U.S. illegally and chose to take their children with them.
—Suzanne Gamboa, NBC news, 19 May 2025
See All Example Sentences for tumor
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Madeline Mitchell, USA Today, 22 May 2025
So when his young grandson develops a brain tumor, Joe needs a way to pay for the boy’s treatment and make amends for his own indifferent parenting.
—Jeannette Catsoulis, New York Times, 22 May 2025
For anyone unfamiliar, a tumor board is a multidisciplinary panel where specialists across the cancer continuum—medical oncologists, surgical oncologists, radiologists, pathologists, radiation oncologists, geneticists and sometimes ethicists—all come together to discuss complex patient cases.
—Sanjay Juneja, Forbes.com, 22 May 2025
The administration has responded to blowback from the children’s expulsions and those of other U.S. citizen minors, including a child with cancer and one recovering from a rare brain tumor, by saying the mothers were in the U.S. illegally and chose to take their children with them.
—Suzanne Gamboa, NBC news, 19 May 2025
See All Example Sentences for tumor
Cite this Entry
“Tumor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tumor. Accessed 10 Jun. 2025.
Copy CitationKids Definition
tumor
noun
tu·mor
ˈt(y)ü-mər 
: an abnormal mass of tissue that arises from normal tissue cells and serves no useful purpose in the body
tumorous
adjective
ˈt(y)üm-(ə-)rəs
Medical Definition
tumor
noun
tu·mor
variants
or chiefly British tumour
: an abnormal benign or malignant new growth of tissue that possesses no physiological function and arises from uncontrolled usually rapid cellular proliferation see cancer sense 1, carcinoma, sarcoma
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