Definition of powder:
the fine particles to which any dry substance is reduced by pounding, grinding, or triturating, or into which it falls by decay; dust; an explosive mixture used in gunnery, blasting, etc.; gunpowder
"grind their bones to powder small. —Shakespeare"
to reduce to fine particles; to pound, grind, or rub into a powder; to comminute; to pulverize; to triturate; to sprinkle with powder, or as with powder; to be sprinkle; as, to powder the hair