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
When Doggart-Bernal’s son required surgery for a brain tumor, writer Brian Lies rallied the community of children’s authors and illustrators to mail him letters and packages.
—Kat Chen, Condé Nast Traveler, 25 Apr. 2026
Sam Butler, who is the mother of a seven-year-old daughter named Florence, was initially diagnosed with giant cell tumors (GCTs) in 2020.
—Staff Author, PEOPLE, 25 Apr. 2026
In the latest check-up following the surgery, Netanyahu revealed in a statement on social media that doctors discovered a malignant tumor in his prostate of less than a centimeter.
—Tal Shalev, CNN Money, 24 Apr. 2026
In December, zoo officials told the public that Mumford had entered hospice care after being diagnosed with an untreatable tumor.
—Kristi Miller, Twin Cities, 24 Apr. 2026
See All Example Sentences for tumor
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Kat Chen, Condé Nast Traveler, 25 Apr. 2026
Sam Butler, who is the mother of a seven-year-old daughter named Florence, was initially diagnosed with giant cell tumors (GCTs) in 2020.
—Staff Author, PEOPLE, 25 Apr. 2026
In the latest check-up following the surgery, Netanyahu revealed in a statement on social media that doctors discovered a malignant tumor in his prostate of less than a centimeter.
—Tal Shalev, CNN Money, 24 Apr. 2026
In December, zoo officials told the public that Mumford had entered hospice care after being diagnosed with an untreatable tumor.
—Kristi Miller, Twin Cities, 24 Apr. 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 Apr. 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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