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
Linder, a former teacher, doesn't work anymore due to a host of medical issues — including treatment for a brain tumor and its effects, and Parkinsonism, a neurological disorder that causes Parkinson's-like symptoms.
—Greg Iacurci, CNBC, 24 Feb. 2026
Several popular peptides work by enhancing the body’s response to growth hormone, which doctors say could have an unintended consequence of promoting tumor growth.
—Dominique Mosbergen, Time, 24 Feb. 2026
The torso scan looks for solid tumors (as early as stage 1) and metabolic disorders, plus non-cancerous conditions like cysts and hematomas.
—David Oliver, USA Today, 23 Feb. 2026
More serious risks, including thyroid tumors and pancreatitis, are also listed in the drug's safety warnings.
—Shafiq Najib, ABC News, 23 Feb. 2026
See All Example Sentences for tumor
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Greg Iacurci, CNBC, 24 Feb. 2026
Several popular peptides work by enhancing the body’s response to growth hormone, which doctors say could have an unintended consequence of promoting tumor growth.
—Dominique Mosbergen, Time, 24 Feb. 2026
The torso scan looks for solid tumors (as early as stage 1) and metabolic disorders, plus non-cancerous conditions like cysts and hematomas.
—David Oliver, USA Today, 23 Feb. 2026
More serious risks, including thyroid tumors and pancreatitis, are also listed in the drug's safety warnings.
—Shafiq Najib, ABC News, 23 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 27 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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