defpoint是什么意思啊?前面加个def还有什么说法吗?

definition points

When you create dimensions in IntelliCAD or AutoCAD, the dimensioning components such as extension lines, arrowheads, dimension lines, and dimension text are placed on the on the current layer. The first time dimensions are added to a drawing, IntelliCAD 98 also creates a special layer named "DEFPOINTS". This layer holds the "definition points" for the dimension. By default this layer does not and cannot be made to print.