What is "blast orifice"

Blast \Blast\ (bl[.a]st), n. [AS. bl[=ae]st a puff of wind, a blowing; akin to Icel. bl[=a]str, OHG. bl[=a]st, and fr. a verb akin to Icel. bl[=a]sa to blow, OHG. bl[^a]san, Goth. bl[=e]san (in comp.); all prob. from the same root as E. blow. See Blow to eject air.]

1. A violent gust of wind.

   And see where surly Winter passes off, Far to the north, and calls his ruffian blasts; His blasts obey, and quit the howling hill.
   --Thomson.

2. A forcible stream of air from an orifice, as from a bellows, the mouth, etc. Hence: The continuous blowing to which one charge of ore or metal is subjected in a furnace; as, to melt so many tons of iron at a blast.

   Note: The terms hot blast and cold blast are employed to designate whether the current is heated or not heated before entering the furnace. A blast furnace is said to be in blast while it is in operation, and out of blast when not in use.

3. The exhaust steam from and engine, driving a column of air out of a boiler chimney, and thus creating an intense draught through the fire; also, any draught produced by the blast.

4. The sound made by blowing a wind instrument; strictly, the sound produces at one breath.

   One blast upon his bugle horn Were worth a thousand men.
   --Sir W. Scott.

   The blast of triumph o'er thy grave.
   --Bryant.

5. A sudden, pernicious effect, as if by a noxious wind, especially on animals and plants; a blight.

   By the blast of God they perish.
   --Job iv. 9.

   Virtue preserved from fell destruction's blast.
   --Shak.

6. The act of rending, or attempting to rend, heavy masses of rock, earth, etc., by the explosion of gunpowder, dynamite, etc.; also, the charge used for this purpose. ``Large blasts are often used.''
   --Tomlinson.

7. A flatulent disease of sheep.

   Blast furnace, a furnace, usually a shaft furnace for smelting ores, into which air is forced by pressure.

   Blast hole, a hole in the bottom of a pump stock through which water enters.

   Blast nozzle, a fixed or variable orifice in the delivery end of a blast pipe; -- called also blast orifice.

   In full blast, in complete operation; in a state of great activity. See Blast, n., 2. [Colloq.]