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
Pancreatic cancer is often diagnosed at a late stage because early pancreatic tumors usually cause no specific symptoms, and there is no effective routine screening test.
—Oren Oppenheim, ABC News, 23 Dec. 2025
Jasmine Ramirez, 14, spent most of her life with a rare lymphomatous tumor that affected her left leg, according to ABC affiliate WFTS.
—Abigail Adams, PEOPLE, 23 Dec. 2025
The 72-year-old two-time Grammy Award winner previously revealed that he was diagnosed with glioblastoma in December 2023 after undergoing emergency surgery that resulted in doctors removing Bolton’s brain tumor in its entirety.
—Ashley Hume, FOXNews.com, 22 Dec. 2025
This effect appears to result from enhancing the immune system at precisely the right time, enabling it to eliminate tumors more effectively.
—Lisa Jarvis, Twin Cities, 20 Dec. 2025
See All Example Sentences for tumor
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Oren Oppenheim, ABC News, 23 Dec. 2025
Jasmine Ramirez, 14, spent most of her life with a rare lymphomatous tumor that affected her left leg, according to ABC affiliate WFTS.
—Abigail Adams, PEOPLE, 23 Dec. 2025
The 72-year-old two-time Grammy Award winner previously revealed that he was diagnosed with glioblastoma in December 2023 after undergoing emergency surgery that resulted in doctors removing Bolton’s brain tumor in its entirety.
—Ashley Hume, FOXNews.com, 22 Dec. 2025
This effect appears to result from enhancing the immune system at precisely the right time, enabling it to eliminate tumors more effectively.
—Lisa Jarvis, Twin Cities, 20 Dec. 2025
See All Example Sentences for tumor
Cite this Entry
“Tumor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tumor. Accessed 24 Dec. 2025.
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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