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
Drug test discovers tumor Broncos linebacker Alex Singleton was randomly selected for a drug test two weeks ago, a routine thing under the NFL’s program.
—Chris Branch, New York Times, 11 Nov. 2025
In July, Sanders announced doctors had removed his bladder after the discovery of a tumor.
—Jackson Thompson, FOXNews.com, 9 Nov. 2025
But when testing the bespoke shots in animals, Grippin noticed that even the placebo shots — which contained mRNA entirely unrelated to the cancer — also activated the immune system to kill tumors.
—Lisa Jarvis, Twin Cities, 8 Nov. 2025
One tumor is centrally located in the middle of her lobes.
—Lucy Notarantonio, MSNBC Newsweek, 8 Nov. 2025
See All Example Sentences for tumor
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Chris Branch, New York Times, 11 Nov. 2025
In July, Sanders announced doctors had removed his bladder after the discovery of a tumor.
—Jackson Thompson, FOXNews.com, 9 Nov. 2025
But when testing the bespoke shots in animals, Grippin noticed that even the placebo shots — which contained mRNA entirely unrelated to the cancer — also activated the immune system to kill tumors.
—Lisa Jarvis, Twin Cities, 8 Nov. 2025
One tumor is centrally located in the middle of her lobes.
—Lucy Notarantonio, MSNBC Newsweek, 8 Nov. 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 14 Nov. 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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