Source : Webster's Revised Unabridged Dictionary (1913)

Powder \Pow"der\, n. [OE. poudre, pouldre, F. poudre, OF. also
   poldre, puldre, L. pulvis, pulveris: cf. pollen fine flour,
   mill dust, E. pollen. Cf. {Polverine}, {Pulverize}.]
   1. The fine particles to which any dry substance is reduced
      by pounding, grinding, or triturating, or into which it
      falls by decay; dust.

            Grind their bones to powder small.    --Shak.

   2. An explosive mixture used in gunnery, blasting, etc.;
      gunpowder. See {Gunpowder}.

   {Atlas powder}, {Baking powder}, etc. See under {Atlas},
      {Baking}, etc.

   {Powder down} (Zo["o]l.), the peculiar dust, or exfoliation,
      of powder-down feathers.

   {Powder-down feather} (Zo["o]l.), one of a peculiar kind of
      modified feathers which sometimes form patches on certain
      parts of some birds. They have a greasy texture and a
      scaly exfoliation.

   {Powder-down patch} (Zo["o]l.), a tuft or patch of
      powder-down feathers.

   {Powder hose}, a tube of strong linen, about an inch in
      diameter, filled with powder and used in firing mines.
      --Farrow.

   {Powder hoy} (Naut.), a vessel specially fitted to carry
      powder for the supply of war ships. They are usually
      painted red and carry a red flag.

   {Powder magazine}, or {Powder room}. See {Magazine}, 2.

   {Powder mine}, a mine exploded by gunpowder. See {Mine}.

   {Powder monkey} (Naut.), a boy formerly employed on war
      vessels to carry powder; a powder boy.

   {Powder post}. See {Dry rot}, under {Dry}.

   {Powder puff}. See {Puff}, n.

Baking \Bak"ing\, n.
   1. The act or process of cooking in an oven, or of drying and
      hardening by heat or cold.

   2. The quantity baked at once; a batch; as, a baking of
      bread.

   {Baking powder}, a substitute for yeast, usually consisting
      of an acid, a carbonate, and a little farinaceous matter.

Source : WordNet®

baking powder
     n : any of various powdered mixtures used in baking as a
         substitute for yeast