Learner's definition of CANCER
1 : a serious disease caused by cells that are not normal and that can spread to one or many parts of the body
He was diagnosed with cancer.
She learned that she has cancer.
Eating certain foods may help reduce the risk of cancer.
[count] — often used before another noun
2 [count] : something bad or dangerous that causes other bad things to happen — usually singular
3 a [noncount] : the fourth sign of the zodiac that comes between Gemini and Leo and has a crab as its symbol b [count] : a person born under the sign of Cancer : a person born between June 22nd and July 22nd