The term geometric primitive in computer graphics and CAD systems is used in various senses, with common meaning of atomic geometric objects the system can handle (draw, store).
Sometimes the subroutines that draw the corresponding objects are called "geometric primitives" as well.
The most "primitive" primitives are point and straight line segment. In fact, they were sufficient for early vector graphics systems.
Modern 2D computer graphics systems may operate with primitives which are lines (segments of straight lines, circles and more complicated curves), as well as shapes (boxes, arbitrary polygons, circles).
In constructive solid geometry, primitives are simple geometric shapes such as a cube, cylinder, sphere, cone, pyramid, torus.
