Applying it in spherical coordinates to the function "one over r" gives a delta function.  
Applying it in spherical coordinates to the function "one over r" gives a delta function.  It is the operator appearing in the vector wave equation and Poisson's equation while in one Cartesian dimension it's just a second derivative.  Equal to the divergence of the gradient is, for ten points, what scalar operator often written as "del-squared".
Applying it in spherical coordinates to the function "one over r" gives a delta function.  
Laplacian (accept del-squared before it's mentioned)