The Collaborative International Dictionary of English v.0.48:

Infusion \In*fu"sion\, n. [L. infusio a pouring in: cf. F.
   infusion. See Infuse, v. t.]
   1. The act of infusing, pouring in, or instilling;
      instillation; as, the infusion of good principles into the
      mind; the infusion of ardor or zeal.
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            Our language has received innumerable elegancies and
            improvements from that infusion of Hebraisms.
                                                  --Addison.
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   2. That which is infused; suggestion; inspiration.
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            His folly and his wisdom are of his own growth, not
            the echo or infusion of other men.    --Swift.
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   3. The act of plunging or dipping into a fluid; immersion.
      [Obs.] "Baptism by infusion." --Jortin.
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   4. (Pharmacy)
      (a) The act or process of steeping or soaking any
          substance in water in order to extract its active
          principles.
      (b) The liquid extract obtained by this process.
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                Sips meek infusion of a milder herb. --Cowper.
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WordNet (r) 3.0 (2006):

infusion
    n 1: a solution obtained by steeping or soaking a substance
         (usually in water) [syn: infusion, extract]
    2: the process of extracting certain active properties (as a
       drug from a plant) by steeping or soaking (usually in water)
    3: (medicine) the passive introduction of a substance (a fluid
       or drug or electrolyte) into a vein or between tissues (as by
       gravitational force)
    4: the act of infusing or introducing a certain modifying
       element or quality; "the team's continued success is
       attributable to a steady infusion of new talent"