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
She was diagnosed with a brain tumor in November, and through fundraisers and a GoFundMe account, donations for medical expenses have topped $125,000.
—Gary Curreri, Sun Sentinel, 17 May 2026
Even after Jovi's tumor was successfully removed, one of her doctors paid her a visit to check on her recovery weeks later.
—Desiree Anello, PEOPLE, 16 May 2026
My cancer was so silent that two gynecologists hadn’t considered it as a possible diagnosis, and at least one radiologist had entirely missed my tumor—as wide as a peach and as long as my hand.
—Nami Mun, The Atlantic, 16 May 2026
Prostate biopsies carry high risk of infection, and surgeries to remove tumors can lead to erectile dysfunction, while radiotherapy and other aggressive treatments have life-altering side effects.
—Annalisa Merelli, STAT, 14 May 2026
See All Example Sentences for tumor
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Gary Curreri, Sun Sentinel, 17 May 2026
Even after Jovi's tumor was successfully removed, one of her doctors paid her a visit to check on her recovery weeks later.
—Desiree Anello, PEOPLE, 16 May 2026
My cancer was so silent that two gynecologists hadn’t considered it as a possible diagnosis, and at least one radiologist had entirely missed my tumor—as wide as a peach and as long as my hand.
—Nami Mun, The Atlantic, 16 May 2026
Prostate biopsies carry high risk of infection, and surgeries to remove tumors can lead to erectile dysfunction, while radiotherapy and other aggressive treatments have life-altering side effects.
—Annalisa Merelli, STAT, 14 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 19 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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