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.
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            An unalterable fixation of resolution.
                                                  --Killingbeck.
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            To light, created in the first day, God gave no
            proper place or fixation.             --Sir W.
                                                  Raleigh.
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            Marked stiffness or absolute fixation of a joint.
                                                  --Quain.
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            A fixation and confinement of thought to a few
            objects.                              --Watts.
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   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.
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   3. The act or process of ceasing to be fluid and becoming
      firm. --Glanvill.
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   4. A state of resistance to evaporation or volatilization by
      heat; -- said of metals. --Bacon.
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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]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "fixation":
   Freudian fixation, anchorage, arrest, arrestation,
   arrested development, arrestment, blockage, blocking, check,
   clogging, closing up, closure, colonization, complex, compulsion,
   confirmation, constriction, cramp, craze, deep-rootedness,
   deep-seatedness, delay, detainment, detention, embedment,
   entrenchment, establishment, fascination, father fixation, fetish,
   fixed idea, fixedness, fixity, fixture, foot-dragging, foundation,
   hampering, hang-up, hindering, hindrance, holdback, holdup,
   hypercathexis, idee fixe, immobility, impediment, implantation,
   inaction, inactivity, inauguration, infantile fixation,
   infatuation, infixion, inhibition, initiation, installation,
   installment, interference, interruption, investiture, inveteracy,
   irresistible impulse, kick, let, libido fixation, lodgment, mania,
   monomania, mooring, morbid drive, mother fixation, motionlessness,
   negativism, nuisance value, obsession, obsessive compulsion,
   obstruction, obstructionism, occlusion, opposition,
   parent fixation, peopling, plantation, population, possession,
   pregenital fixation, preoccupation, prepossession, regression,
   repression, resistance, restraint, restriction, retardation,
   retardment, retreat to immaturity, ruling passion, setback,
   settlement, settling, squeeze, stabilization, stranglehold,
   stricture, suppression, thing, tic