Source : Webster's Revised Unabridged Dictionary (1913)

Infection \In*fec"tion\, n. [Cf. F. infection, L. infectio a
   dyeing.]
   1. The act or process of infecting.

            There was a strict order against coming to those
            pits, and that was only to prevent infection. --De
                                                  Foe.

   2. That which infects, or causes the communicated disease;
      any effluvium, miasm, or pestilential matter by which an
      infectious disease is caused.

            And that which was still worse, they that did thus
            break out spread the infection further by their
            wandering about with the distemper upon them. --De
                                                  Foe.

   3. The state of being infected; contamination by morbific
      particles; the result of infecting influence; a prevailing
      disease; epidemic.

            The danger was really very great, the infection
            being so very violent in London.      --De Foe.

   4. That which taints or corrupts morally; as, the infection
      of vicious principles.

            It was her chance to light Amidst the gross
            infections of those times.            --Daniel.

   5. (Law) Contamination by illegality, as in cases of
      contraband goods; implication.

   6. Sympathetic communication of like qualities or emotions;
      influence.

            Through all her train the soft infection ran.
                                                  --Pope.

            Mankind are gay or serious by infection. --Rambler.

   Syn: {Infection}, {Contagion}.

   Usage: Infection is often used in a definite and limited
          sense of the transmission of affections without direct
          contact of individuals or immediate application or
          introduction of the morbific agent, in
          contradistinction to contagion, which then implies
          transmission by direct contact. Quain. See
          {Contagious}.

Source : WordNet®

infection
     n 1: the pathological state resulting from the invasion of the
          body by pathogenic microorganisms
     2: (phonetics) the alteration of a speech sound under the
        influence of a neighboring sound
     3: (medicine) the invasion of the body by pathogenic
        microorganisms and their multiplication which can lead to
        tissue damage and disease
     4: an incident in which an infectious disease is transmitted
        [syn: {contagion}, {transmission}]
     5: the communication of an attitude or emotional state among a
        number of people; "a contagion of mirth"; "the infection
        of his enthusiasm for poetry" [syn: {contagion}]
     6: moral corruption or contamination; "ambitious men are led
        astray by an infection that is almost unavoidable"
     7: (international law) illegality that taints or contaminates a
        ship or cargo rendering it liable to seizure