Back pressure

Pressure \Pres"sure\ (?; 138), n. [OF., fr. L. pressura, fr.
   premere. See 4th {Press}.]
   1. The act of pressing, or the condition of being pressed;
      compression; a squeezing; a crushing; as, a pressure of
      the hand.
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   2. A contrasting force or impulse of any kind; as, the
      pressure of poverty; the pressure of taxes; the pressure
      of motives on the mind; the pressure of civilization.
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            Where the pressure of danger was not felt.
                                                  --Macaulay.
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   3. Affliction; distress; grievance.
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            My people's pressures are grievous.   --Eikon
                                                  Basilike.
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            In the midst of his great troubles and pressures.
                                                  --Atterbury.
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   4. Urgency; as, the pressure of business.
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   5. Impression; stamp; character impressed.
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            All saws of books, all forms, all pressures past.
                                                  --Shak.
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   6. (Mech.) The action of a force against some obstacle or
      opposing force; a force in the nature of a thrust,
      distributed over a surface, often estimated with reference
      to the amount upon a unit's area.
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   7. Electro-motive force.
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   {Atmospheric pressure}, {Center of pressure}, etc. See under
      {Atmospheric}, {Center}, etc.

   {Back pressure} (Steam engine), pressure which resists the
      motion of the piston, as the pressure of exhaust steam
      which does not find free outlet.

   {Fluid pressure}, pressure like that exerted by a fluid. It
      is a thrust which is normal and equally intense in all
      directions around a point. --Rankine.

   {Pressure gauge}, a gauge for indicating fluid pressure; a
      manometer.
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Back \Back\, a.
   1. Being at the back or in the rear; distant; remote; as, the
      back door; back settlements.
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   2. Being in arrear; overdue; as, back rent.
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   3. Moving or operating backward; as, back action.
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   {Back blocks}, Australian pastoral country which is remote
      from the seacoast or from a river. [Webster 1913 Suppl.]
      

   {Back charges}, charges brought forward after an account has
      been made up.

   {Back filling} (Arch.), the mass of materials used in filling
      up the space between two walls, or between the inner and
      outer faces of a wall, or upon the haunches of an arch or
      vault.

   {Back pressure}. (Steam Engine) See under {Pressure}.

   {Back rest}, a guide attached to the slide rest of a lathe,
      and placed in contact with the work, to steady it in
      turning.

   {Back slang}, a kind of slang in which every word is written
      or pronounced backwards; as, nam for man.

   {Back stairs}, stairs in the back part of a house; private
      stairs. Also used adjectively. See {Back stairs},
      {Backstairs}, and {Backstair}, in the Vocabulary.

   {Back step} (Mil.), the retrograde movement of a man or body
      of men, without changing front.

   {Back stream}, a current running against the main current of
      a stream; an eddy.

   {To take the back track}, to retrace one's steps; to retreat.
      [Colloq.]
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