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 test monitors treatment response and cancer recurrence by detecting circulating tumor DNA, giving physicians real-time insights into treatment effectiveness.
—
Sasirekha Subramanian,
Forbes.com,
29 June 2026
The 11-year-old was diagnosed with an aggressive spinal tumor at the age of three and is paralyzed from the waist down.
—
Taijuan Moorman,
USA Today,
29 June 2026
Rush University, which removed the tumors, analyzed each one.
—
John Lippert,
Chicago Tribune,
28 June 2026
There were some additional cancer cells in tissue near the tumor that needed to be scraped out.
—
Matthew Futterman,
New York Times,
28 June 2026
See All Example Sentences for tumor
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Sasirekha Subramanian,
Forbes.com,
29 June 2026
The 11-year-old was diagnosed with an aggressive spinal tumor at the age of three and is paralyzed from the waist down.
—
Taijuan Moorman,
USA Today,
29 June 2026
Rush University, which removed the tumors, analyzed each one.
—
John Lippert,
Chicago Tribune,
28 June 2026
There were some additional cancer cells in tissue near the tumor that needed to be scraped out.
—
Matthew Futterman,
New York Times,
28 June 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 3 Jul. 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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