The Collaborative International Dictionary of English v.0.48:

Effusion \Ef*fu"sion\, n. [L. effusio: cf. F. effusion.]
   1. The act of pouring out; as, effusion of water, of blood,
      of grace, of words, and the like.
      [1913 Webster]

            To save the effusion of my people's blood. --Dryden.
      [1913 Webster]

   2. That which is poured out, literally or figuratively.
      [1913 Webster]

            Wash me with that precious effusion, and I shall be
            whiter than sow.                      --Eikon
                                                  Basilike.
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            The light effusions of a heedless boy. --Byron.
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   3. (Pathol.)
      (a) The escape of a fluid out of its natural vessel,
          either by rupture of the vessel, or by exudation
          through its walls. It may pass into the substance of
          an organ, or issue upon a free surface.
      (b) The liquid escaping or exuded.
          [1913 Webster]

WordNet (r) 3.0 (2006):

effusion
    n 1: an unrestrained expression of emotion [syn: effusion,
         gush, outburst, blowup, ebullition]
    2: flow under pressure