A genus of decapod Crustacea, including some of the most common shore crabs of Europe and North America, as the rock crab, Jonah crab, etc. See Crab.
- Any of various malignant neoplasms characterized by the proliferation of anaplastic cells that tend to invade surrounding tissue and metastasize to new body sites.
- The pathological condition characterized by such growths.
- A pernicious, spreading evil: A cancer of bigotry spread through the community.