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
While the trailer focuses in on Will and Ulster's latest encounter, a pregnant Angie, Faith (Iantha Richardson), Nico (Cora Lu Tran), Wilks (Kevin Daniels) and even Ormewood (Jake McLaughlin), who was last seen in the middle of a medical crisis due to a brain tumor, all make appearances, as well.
—Sabienna Bowman, PEOPLE, 30 Dec. 2025
Plus, a new blood test that can show when tumors are becoming resistant to standard treatments is changing how doctors treat the cancer.
—Helen Carefoot, Flow Space, 26 Dec. 2025
Pancreatic cancer is often diagnosed at a late stage because early pancreatic tumors usually cause no specific symptoms, and there is no effective routine screening test.
—Oren Oppenheim, ABC News, 23 Dec. 2025
The result was a form of incisionless surgery, a way to wipe out tumors without scalpels, radiation, or heat.
—IEEE Spectrum, 22 Dec. 2025
See All Example Sentences for tumor
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Sabienna Bowman, PEOPLE, 30 Dec. 2025
Plus, a new blood test that can show when tumors are becoming resistant to standard treatments is changing how doctors treat the cancer.
—Helen Carefoot, Flow Space, 26 Dec. 2025
Pancreatic cancer is often diagnosed at a late stage because early pancreatic tumors usually cause no specific symptoms, and there is no effective routine screening test.
—Oren Oppenheim, ABC News, 23 Dec. 2025
The result was a form of incisionless surgery, a way to wipe out tumors without scalpels, radiation, or heat.
—IEEE Spectrum, 22 Dec. 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 1 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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