The Collaborative International Dictionary of English v.0.48:

Flotation \Flo*ta"tion\, n. [Cf. F. flottation a floating,
   flottaison water line, fr. flotter to float. See Flotilla.]
   1. The act, process, or state of floating.
      [1913 Webster]

   2. The science of floating bodies.
      [1913 Webster]

   3. (Com. & Finance) Act of financing, or floating, a
      commercial venture or an issue of bonds, stock, or the
      like.
      [Webster 1913 Suppl.]

   Center of flotation. (Shipbuilding)
      (a) The center of any given plane of flotation.
      (b) More commonly, the middle of the length of the load
          water line. --Rankine.

   Plane of flotation, or Line of flotation, the plane or
      line in which the horizontal surface of a fluid cuts a
      body floating in it. See Bearing, n., 9
      (c) .

   Surface of flotation (Shipbuilding), the imaginary surface
      which all the planes of flotation touch when a vessel
      rolls or pitches; the envelope of all such planes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

center of flotation
    n 1: the center of gravity of a floating object [syn: center of
         flotation, centre of flotation]