The Collaborative International Dictionary of English v.0.48:

Empiricism \Em*pir"i*cism\, n.
   1. The method or practice of an empiric; pursuit of knowledge
      by observation and experiment.
      [1913 Webster]

   2. Specifically, a practice of medicine founded on mere
      experience, without the aid of science or a knowledge of
      principles; ignorant and unscientific practice;
      charlatanry; quackery.
      [1913 Webster]

   3. (Metaph.) The philosophical theory which attributes the
      origin of all our knowledge to experience.
      [1913 Webster]

WordNet (r) 3.0 (2006):

empiricism
    n 1: (philosophy) the doctrine that knowledge derives from
         experience [syn: empiricism, empiricist philosophy,
         sensationalism]
    2: the application of empirical methods in any art or science
    3: medical practice and advice based on observation and
       experience in ignorance of scientific findings [syn:
       quackery, empiricism]