in Astronomy, one of the twelve signs, represented on the globe in the form of a crab, and thus marked (♋) in books. The reason generally assigned for its name, as well as figure, is a supposed resemblance which the sun's motion in this sign bears to that of the crab-fish. As the latter walks backwards, so the former, in this part of his course, begins to go backwards, or recede from us; though the disposition of stars in this sign is by others supposed to have given the first hint of the representation of a crab.

Tropic of Cancer, in Astronomy, a lesser circle of the sphere parallel to the equator, and passing through the beginning of the sign Cancer.