Clumping, or random density inhomogeneities
Creates a porous wind, potentially with paths having lower column densities (but other paths higher, if mass is conserved)
Can reduce average optical depth of the wind appreciably only if individual clumps are optically thick: Then the atomic cross section in the opacity is replaced by the physical cross section of the clump
Clumps would therefore have to be quite large

Non-isotropic clumping can have an effect  on line profilesÉ