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
Ron explains that the tumor started growing back in 2018 and past doctors were unsure about how to approach such a challenging facial reconstruction.
—Vanessa Etienne, PEOPLE, 28 Oct. 2025
The scans are often used to check for aneurysms of cerebral vessels, conditions of the eye and inner ear, multiple sclerosis, spinal cord conditions, stroke, tumors and brain injury from trauma.
—Jasmine Laws, MSNBC Newsweek, 27 Oct. 2025
Microcatheters are already critical for lifesaving procedures such as clearing clogged arteries, stopping bleeding, or delivering drugs directly to tumors.
—Neetika Walter, Interesting Engineering, 27 Oct. 2025
Every three months, Brunty-Barojas has been undergoing surgery to remove colorectal tumors that, left unattended, could turn cancerous.
—Lauren Villagran, USA Today, 26 Oct. 2025
See All Example Sentences for tumor
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Vanessa Etienne, PEOPLE, 28 Oct. 2025
The scans are often used to check for aneurysms of cerebral vessels, conditions of the eye and inner ear, multiple sclerosis, spinal cord conditions, stroke, tumors and brain injury from trauma.
—Jasmine Laws, MSNBC Newsweek, 27 Oct. 2025
Microcatheters are already critical for lifesaving procedures such as clearing clogged arteries, stopping bleeding, or delivering drugs directly to tumors.
—Neetika Walter, Interesting Engineering, 27 Oct. 2025
Every three months, Brunty-Barojas has been undergoing surgery to remove colorectal tumors that, left unattended, could turn cancerous.
—Lauren Villagran, USA Today, 26 Oct. 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 1 Nov. 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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