tumor

noun

tu·​mor ˈtü-mər 

ˈtyü-

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

tumoral

ˈtü-mə-rəl 

ˈtyü-

adjective

tumorlike

ˈtü-mər-ˌlīk 

ˈtyü-

adjective

Synonyms of tumor

• lump
• neoplasm
• cyst
• growth
• carcinoma

Examples of tumor in a Sentence

the scan showed a small tumor in her abdomen

Recent Examples on the Web

Most breast cancer cases in older women are estrogen-receptor positive (ER+), meaning that tumor cells have receptors that bind to estrogen and trigger cancer growth. — Allessandra Dicorato, STAT, 8 Oct. 2026

He was diagnosed with a cancerous tumor in his kidney in 2016, and cleared that. — Fort Worth Star-Telegram, 6 Oct. 2026

Once breast cancer is diagnosed, understanding the biology of the tumor can help guide treatment. — Baptist Health, Miami Herald, 30 Sep. 2026

Many patients could be helped by new drugs that disable the genes fueling their tumors. — Gina Kolata, New York Times, 30 Sep. 2026

Word History

Etymology

Middle English tumour, from Latin tumor, from tumēre

First Known Use

15th century, in the meaning defined at sense 2

Phrases Containing tumor

• anti-tumor
• tumor load
• tumor necrosis factor
• tumor suppressor gene

Rhymes for tumor

• boomer
• humor
• humour
• plumer
• rumor
• rumour
• tumour
• antitumor
• pseudotumor
• consumer
• perfumer

Kids 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

ˈt(y)üm-(ə-)rəs

adjective

Medical Definition

tumor

noun

tu·​mor

variants or chiefly British tumour

ˈt(y)ü-mər 

: 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

tumorlike

-ˌlīk 

adjective