a kabuki brush is a short full brush that... according to my brother... looks somewhat like a mushroom =\
You can find it on the MAC website (#182). The 187 is the stippling brush that's good for use on very pigmented products (and many other things hehe). the 182 is more for buffing things out, blending etc. They're very different brushes... the 187 picks up a small amount of product and allows you to control its intensity and application more closely, whereas if the 182 were to be used for the same thing, you'd end up with a huge extremely dark streak of whatever the pigmented powder you were using was.
I use the 182 to fix those mistakes... to blend and buff out the harsh lines and soften the intensity
Here's the MAC description of the 182 brush: A full, dome-shaped brush of extra soft goat hair. Specially created to flawlessly blend powder onto the skin for an immaculate polished finish. Excellent for all M·A·C powders and pigments.