a piece of material that has a sticky coating on it

A fabric impregnated with a tacky substance that is used to remove dust from a surface after sanding or rubbing down, and prior to further painting. It should be stored in an airtight container to preserve its tackiness.

A tack cloth is a piece of fabric impregnated with varnish, oil or a solvent so that it remains permanently sticky under proper storage and can be used to remove minute dust particles from a surface to be finished.