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 tumor was removed, however due to its locations and the extensive surgical procedure there were changes in her personality afterward.
—R. Eric Thomas, Denver Post, 19 Mar. 2026
If a colonoscopy back positive for colon cancer, surgery is typically done to remove the tumors or portions of the colon, followed by chemotherapy or other cancer treatment, depending on how advanced the cancer is, Olson and Verma said.
—Miriam Fauzia, Dallas Morning News, 19 Mar. 2026
The two organizations recognized the compound could fight tumors caused by a rare genetic disorder, so Pfizer licensed it to a new spin-off, SpringWorks Therapeutics.
—Annette Bakker, Fortune, 19 Mar. 2026
Judy Wood has Ledderhose disease, a rare and aggressive genetic condition that causes fibrous tumors to grow on the soles of the feet.
—Josh Taylor, CBS News, 19 Mar. 2026
See All Example Sentences for tumor
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R. Eric Thomas, Denver Post, 19 Mar. 2026
If a colonoscopy back positive for colon cancer, surgery is typically done to remove the tumors or portions of the colon, followed by chemotherapy or other cancer treatment, depending on how advanced the cancer is, Olson and Verma said.
—Miriam Fauzia, Dallas Morning News, 19 Mar. 2026
The two organizations recognized the compound could fight tumors caused by a rare genetic disorder, so Pfizer licensed it to a new spin-off, SpringWorks Therapeutics.
—Annette Bakker, Fortune, 19 Mar. 2026
Judy Wood has Ledderhose disease, a rare and aggressive genetic condition that causes fibrous tumors to grow on the soles of the feet.
—Josh Taylor, CBS News, 19 Mar. 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 21 Mar. 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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