The Collaborative International Dictionary of English v.0.48:

Preoccupation \Pre*oc`cu*pa"tion\, n. [L. praeoccupatio: cf. F.
   pr['e]occupation.]
   1. The act of preoccupying, or taking possession of
      beforehand; the state of being preoccupied; prepossession.
      [1913 Webster]

   2. Anticipation of objections. [R.] --South.
      [1913 Webster]

WordNet (r) 3.0 (2006):

preoccupation
    n 1: an idea that preoccupies the mind and holds the attention
    2: the mental state of being preoccupied by something [syn:
       preoccupation, preoccupancy, absorption, engrossment]
    3: the act of taking occupancy before someone else does [syn:
       preoccupancy, preoccupation]