The Collaborative International Dictionary of English v.0.48:

Pressure cooker \Pressure cooker\
   1. (Cookery) a pot with a lid which may be tightly bound to
      the bottom part, forming a vessel which can withstand some
      gas pressure from within. It is used to heat foods in
      water or steam to a temperature somewhat above the boiling
      point of water, allowing the cooking process to be
      accomplished more quickly than otherwise.
      [PJC]

   2. Fig., a situation involving intense psychological pressure
      due to multiple urgent demands, as in certain job
      situations.
      [PJC]

WordNet (r) 3.0 (2006):

pressure cooker
    n 1: autoclave for cooking at temperatures above the boiling
         point of water