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
But a new study suggests that artificial intelligence might be able to find signs of the disease before tumors are visible on a scan.
—Aria Bendix, NBC news, 2 May 2026
The tumors caused by the cancer grow slowly.
—Kerry Breen, CBS News, 2 May 2026
Previous research by the same team indicated that elevated levels of PFOA and PFOS also were connected to other childhood cancers, including acute myeloid leukemia and Wilms tumor.
—Rachel Fobar, Oc Register, 1 May 2026
Scans eventually revealed a tumor in her bowel, and although Fyfe underwent surgery, the cancer has since spread and is now considered inoperable, the fundraiser states.
—Angelique Brenes, PEOPLE, 1 May 2026
See All Example Sentences for tumor
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Aria Bendix, NBC news, 2 May 2026
The tumors caused by the cancer grow slowly.
—Kerry Breen, CBS News, 2 May 2026
Previous research by the same team indicated that elevated levels of PFOA and PFOS also were connected to other childhood cancers, including acute myeloid leukemia and Wilms tumor.
—Rachel Fobar, Oc Register, 1 May 2026
Scans eventually revealed a tumor in her bowel, and although Fyfe underwent surgery, the cancer has since spread and is now considered inoperable, the fundraiser states.
—Angelique Brenes, PEOPLE, 1 May 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 4 May. 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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