The Collaborative International Dictionary of English v.0.48:

Fixation \Fix*a"tion\ (f[i^]ks*[=a]"sh[u^]n), n. [Cf. F.
   fixation.]
   1. The act of fixing, or the state of being fixed.
      [1913 Webster]

            An unalterable fixation of resolution.
                                                  --Killingbeck.
      [1913 Webster]

            To light, created in the first day, God gave no
            proper place or fixation.             --Sir W.
                                                  Raleigh.
      [1913 Webster]

            Marked stiffness or absolute fixation of a joint.
                                                  --Quain.
      [1913 Webster]

            A fixation and confinement of thought to a few
            objects.                              --Watts.
      [1913 Webster]

   2. The act of uniting chemically with a solid substance or in
      a solid form; reduction to a non-volatile condition; --
      said of gaseous elements.
      [1913 Webster]

   3. The act or process of ceasing to be fluid and becoming
      firm. --Glanvill.
      [1913 Webster]

   4. A state of resistance to evaporation or volatilization by
      heat; -- said of metals. --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fixation
    n 1: an abnormal state in which development has stopped
         prematurely [syn: arrested development, fixation,
         infantile fixation, regression]
    2: an unhealthy and compulsive preoccupation with something or
       someone [syn: obsession, fixation]
    3: the activity of fastening something firmly in position
    4: (histology) the preservation and hardening of a tissue sample
       to retain as nearly as possible the same relations they had
       in the living body [syn: fixation, fixing]