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
Instead of waiting for tumors to grow, doctors could use routine blood monitoring to guide treatment changes earlier, extending the time patients live without their disease advancing.
—Lauryn Higgins, Flow Space, 21 Oct. 2025
Initially, it was believed Carter had a stage 1 or 2 Wilms tumor, also known as nephroblastoma, the most common and treatable kidney cancer.
—Tereza Shkurtaj, PEOPLE, 19 Oct. 2025
Treatments for Potentially Resectable Stomach Cancer People with potentially resectable stomach cancer have a cancerous tumor that has grown into more layers of the stomach lining or wall.
—Carrie Madormo, Health, 18 Oct. 2025
The man placed his hand on Williams’ hip, right above his tumor.
—Luca Evans, Denver Post, 17 Oct. 2025
See All Example Sentences for tumor
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Lauryn Higgins, Flow Space, 21 Oct. 2025
Initially, it was believed Carter had a stage 1 or 2 Wilms tumor, also known as nephroblastoma, the most common and treatable kidney cancer.
—Tereza Shkurtaj, PEOPLE, 19 Oct. 2025
Treatments for Potentially Resectable Stomach Cancer People with potentially resectable stomach cancer have a cancerous tumor that has grown into more layers of the stomach lining or wall.
—Carrie Madormo, Health, 18 Oct. 2025
The man placed his hand on Williams’ hip, right above his tumor.
—Luca Evans, Denver Post, 17 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 24 Oct. 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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