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
While 90% of the tumors had microplastics, 70% of noncancerous samples did, too.
—Erika Edwards, NBC news, 2 Apr. 2026
The drugmaker warned that the treatment could cause tumors in the thyroid, including thyroid cancer, warning patients to monitor symptoms such as a lump or swelling in the neck, hoarseness, trouble swallowing or shortness of breath.
—Angelica Stabile, FOXNews.com, 2 Apr. 2026
Roughly 90% of these tumors are diagnosed in patients under 20 years old, often around the onset of puberty, making Tamura an outlier.
—Rachel Hale, USA Today, 31 Mar. 2026
Total gastrectomies had been performed before, in patients whose stomachs were already ridden with tumors—but never routinely in healthy people who did not have cancer and may ultimately never have cancer at all.
—Sarah Zhang, The Atlantic, 31 Mar. 2026
See All Example Sentences for tumor
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Erika Edwards, NBC news, 2 Apr. 2026
The drugmaker warned that the treatment could cause tumors in the thyroid, including thyroid cancer, warning patients to monitor symptoms such as a lump or swelling in the neck, hoarseness, trouble swallowing or shortness of breath.
—Angelica Stabile, FOXNews.com, 2 Apr. 2026
Roughly 90% of these tumors are diagnosed in patients under 20 years old, often around the onset of puberty, making Tamura an outlier.
—Rachel Hale, USA Today, 31 Mar. 2026
Total gastrectomies had been performed before, in patients whose stomachs were already ridden with tumors—but never routinely in healthy people who did not have cancer and may ultimately never have cancer at all.
—Sarah Zhang, The Atlantic, 31 Mar. 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 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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