The Collaborative International Dictionary of English v.0.48:

Systemic \Sys*tem"ic\, a.
   1. Of or relating to a system; common to a system; as, the
      systemic circulation of the blood.
      [1913 Webster]

   2. (Anat. & Physiol.) Of or pertaining to the general system,
      or the body as a whole; as, systemic death, in distinction
      from local death; systemic circulation, in distinction
      from pulmonic circulation; systemic diseases.
      [1913 Webster]

   Systemic death. See the Note under Death, n., 1.
      [1913 Webster]

WordNet (r) 3.0 (2006):

systemic
    adj 1: affecting an entire system; "a systemic poison"