What is AutoLISP? AutoLISP is an interpretive language, so it can be stored in an ASCII text file, loaded, and then executed directly within AutoCAD and its derivatives, which include AutoCAD Map 3D, AutoCAD Architecture and AutoCAD Mechanical. It makes our work is more faster in AutoCAD enviroment. AutoLISP files typically have an .lsp file extension, but they can also have the .mnl file extension. Both LSP and MNL files can be edited with a text editor.