Source : Webster's Revised Unabridged Dictionary (1913)

Low-pressure \Low"-pres`sure\, a.
   Having, employing, or exerting, a low degree of pressure.

   {Low-pressure steam engine}, a steam engine in which low
      steam is used; often applied to a condensing engine even
      when steam at high pressure is used. See {Steam engine}.

Source : WordNet®

low-pressure
     adj : not forceful; "a low-pressure salesman"; "a low-pressure
           campaign"