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
Chaga not only offers many essential nutrients, but it has also been found to boost the immune system, assist with preventing tumors, promote liver and digestive health and reduce inflammation.
—Bestreviews, Mercury News, 5 Feb. 2026
Woodland underwent brain surgery in September 2023 after discovery of a tumor.
—Maddie Hartley, Kansas City Star, 5 Feb. 2026
In April 2025, Silva underwent surgery to remove the tumor on her kidney and was declared cancer-free because the disease was caught so early.
—Vanessa Etienne, PEOPLE, 4 Feb. 2026
Mancini then missed the 2020 season after surgery to remove a malignant tumor from his colon.
—Los Angeles Times, 4 Feb. 2026
See All Example Sentences for tumor
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Bestreviews, Mercury News, 5 Feb. 2026
Woodland underwent brain surgery in September 2023 after discovery of a tumor.
—Maddie Hartley, Kansas City Star, 5 Feb. 2026
In April 2025, Silva underwent surgery to remove the tumor on her kidney and was declared cancer-free because the disease was caught so early.
—Vanessa Etienne, PEOPLE, 4 Feb. 2026
Mancini then missed the 2020 season after surgery to remove a malignant tumor from his colon.
—Los Angeles Times, 4 Feb. 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 6 Feb. 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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