noun

1. a N constellation between Gemini and Leo; the Crab
2. the fourth sign of the zodiac, entered by the sun about June 21: also called the Crab
3. a person born under this sign
   also Cancerian Can·cer′·i·an (-sir′ē ən)
4. 1. a malignant new growth anywhere in the body of a person or animal; malignant tumor: cancers tend to spread locally and to distant parts of the body
   2. any of various diseases characterized by the uncontrolled growth of cells that disrupt body tissue, metabolism, etc.
5. anything bad or harmful that spreads and destroys

Etymology: ME & OE < L, a crab; later, malignant tumor; by dissimilation (? already in IE) < IE *karkar-, redupl. of base *kar-, hard > hard, Gr karbinos, crab, Sans karkara, rough, hard, karkata, crab