A Truncus

1. (biology) The thorax of an insect.
2. (medicine) The trunk (torso) of the human body or other animal body.
3. (medicine) An arterial trunk, such as the truncus arteriosus.
4. (geometry) A curve in the Cartesian plane consisting of all points (x,y) satisfying an equation of the form where a, b, and c are given constants.