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
With this panoramic view of the body, doctors may spot big problems, like a large tumor.
—Matt Fuchs, Time, 9 Apr. 2025
Power Rangers Mystic Force star Peta Rutter died of a brain tumor in 2010, and even more actors who appeared on the series — Edward Laurence Albert, Robert L. Manahan, Machiko Soga, and Richard Genelle — have passed of natural causes.
—Ryan Coleman, EW.com, 7 Apr. 2025
Delaney, who has been public about his own experience with death in losing his toddler-aged son to a brain tumor, and Slate, a comedian with the soul of a poet, are each at their bests here.
—Alison Herman, Variety, 4 Apr. 2025
To check whether tumor cells were secreting something that primed the lungs to host them, Altea-Manzano and colleagues grew pieces of mouse mammary tumor in a dish, then collected the liquid containing all the cellular secretions.
—Amber Dance, Smithsonian Magazine, 4 Apr. 2025
See All Example Sentences for tumor
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Matt Fuchs, Time, 9 Apr. 2025
Power Rangers Mystic Force star Peta Rutter died of a brain tumor in 2010, and even more actors who appeared on the series — Edward Laurence Albert, Robert L. Manahan, Machiko Soga, and Richard Genelle — have passed of natural causes.
—Ryan Coleman, EW.com, 7 Apr. 2025
Delaney, who has been public about his own experience with death in losing his toddler-aged son to a brain tumor, and Slate, a comedian with the soul of a poet, are each at their bests here.
—Alison Herman, Variety, 4 Apr. 2025
To check whether tumor cells were secreting something that primed the lungs to host them, Altea-Manzano and colleagues grew pieces of mouse mammary tumor in a dish, then collected the liquid containing all the cellular secretions.
—Amber Dance, Smithsonian Magazine, 4 Apr. 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 23 Apr. 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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