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
Written and directed by Iyiola in her directorial debut, the film follows Zadie, a successful London florist suffering from fibroids, benign tumors that can develop in the wall of the uterus.
—Stewart Clarke, Deadline, 15 Jan. 2026
More than 600,000 people are expected to die from cancer, with lung, colorectal and pancreatic tumors expected to be the three leading causes.
—Bloomberg, Oc Register, 13 Jan. 2026
Stephen Gruber-Miller At their legislative breakfast on the first day of the new session, Republicans gave a standing ovation to former Senate Majority Leader Jack Whitver, R-Grimes, who stepped down from his leadership post last fall while battling a brain tumor.
—Stephen Gruber-Miller, Des Moines Register, 12 Jan. 2026
Because epithelial cells grow quickly, even a slight mismatch between the rates of cell division and cell death can quickly add up to a tumor or injury.
—Elise Cutts, Quanta Magazine, 12 Jan. 2026
See All Example Sentences for tumor
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Stewart Clarke, Deadline, 15 Jan. 2026
More than 600,000 people are expected to die from cancer, with lung, colorectal and pancreatic tumors expected to be the three leading causes.
—Bloomberg, Oc Register, 13 Jan. 2026
Stephen Gruber-Miller At their legislative breakfast on the first day of the new session, Republicans gave a standing ovation to former Senate Majority Leader Jack Whitver, R-Grimes, who stepped down from his leadership post last fall while battling a brain tumor.
—Stephen Gruber-Miller, Des Moines Register, 12 Jan. 2026
Because epithelial cells grow quickly, even a slight mismatch between the rates of cell division and cell death can quickly add up to a tumor or injury.
—Elise Cutts, Quanta Magazine, 12 Jan. 2026
See All Example Sentences for tumor
Cite this Entry
“Tumor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tumor. Accessed 17 Jan. 2026.
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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