(From "dimension") A keyword in most versions of the BASIC programming language that declares the size of an array. E.g. DIM A(100) declares a one-dimensional array with 101 numeric elements (including A(0)). Visual Basic uses the DIM (or "Dim") statement for any variable declaration, even scalars, e.g. Dim DepartmentNumber As Integer which declares a single (scalar) variable of type Integer.