1 n : discrete particle of dirt or other material. [ASTM F1241] Also see dirt.
2 n (dust) : discrete particle of material that can usually be removed by (nonetching) cleaning. [SEMI M10-89]
3 adj : describes material in small, discrete pieces; anything that is not a fiber and has an aspect ratio of less than 3 to 1. Examples are dusts, fumes, smokes, mists, and fogs. [SEMATECH]