1) To find the residue of a function. The residue at an isolated singular point z0 of a function f(z) is defined as the contour integral of f(z) around C, all over two Pi i, where C is a positively oriented simple closed contour enclosing z0 (and no other singularities of f(z)) and i is the imaginary number defined as (-1)^(1/2). Alternatively, one can define the residue as the coefficient of the z^-1 term in the Laurent series expansion of f(z) about z0.
2) To jizz on that bitch's face.
> Definition 1:
> 1) Residuate that [ho]!
> 2) Dude 1 - "Dude, I can't residuate this function."