AutoLisp is a programming language, a dialect of LISP included with the CAD program Autocad to allow the user to add functionality to the software. It is not included with the "AutoCAD LT" product line.
The language was derived in 1982 from the XLISP dialect of LISP, which was created by David Betz. It's a small language compared to Common Lisp. It has extensions that support the manipulation of graphical entities. The properties of these graphical entities are stored as association lists in which AutoLisp "group codes" are paired with values that indicate properties such as points, radii, colors, layers, linetyptes, etc.