A drawing of a common architectural, mechanical or electronic element that contains parameters about its characteristics. With parametric symbols, the designer as well as the software are able to deal with the object as a real-world entity rather than just lines and polygons.
A Parametric Symbol
The parameters (end of screw, head, etc.) shown in the middle-left part of this dialog from IMSI's parametric symbol library refer to the currently selected hexagon screw. (Image courtesy of IMSI, www.imsisoft.com)