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
Senior author Louise van der Weyden, a staff scientist at the Wellcome Sanger Institute in England, and a team of researchers sequenced the genomes of tumors from almost 500 domestic cats.
—K. R. Callaway, Scientific American, 19 Feb. 2026
Viewers paid rapt attention to Robin Roberts’ journey through treatment tied to myelodysplastic syndrome, a bone marrow disease, in 2012, and, in 2023, kept up with Michael Strahan after his daughter was diagnosed with medulloblastoma, a type of brain tumor.
—Brian Steinberg, Variety, 19 Feb. 2026
Greene, who spoke to his manager as recently as two days before he was found dead, had surgery scheduled to remove a benign tumor near his lungs in the coming days, Edward said.
—Tribune News Service, Baltimore Sun, 19 Feb. 2026
He was scheduled to go in for a procedure to remove a benign tumor near his lung on the day he was found, the outlet said.
—Assistant Editor, Los Angeles Times, 19 Feb. 2026
See All Example Sentences for tumor
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K. R. Callaway, Scientific American, 19 Feb. 2026
Viewers paid rapt attention to Robin Roberts’ journey through treatment tied to myelodysplastic syndrome, a bone marrow disease, in 2012, and, in 2023, kept up with Michael Strahan after his daughter was diagnosed with medulloblastoma, a type of brain tumor.
—Brian Steinberg, Variety, 19 Feb. 2026
Greene, who spoke to his manager as recently as two days before he was found dead, had surgery scheduled to remove a benign tumor near his lungs in the coming days, Edward said.
—Tribune News Service, Baltimore Sun, 19 Feb. 2026
He was scheduled to go in for a procedure to remove a benign tumor near his lung on the day he was found, the outlet said.
—Assistant Editor, Los Angeles Times, 19 Feb. 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 20 Feb. 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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