The Collaborative International Dictionary of English v.0.48:

Infect \In*fect"\, v. t. [imp. & p. p. Infected; p. pr. & vb.
   n. Infecting.] [L. infectus, p. p. of inficere to put or
   dip into, to stain, infect; pref. in- in + facere to make;
   cf. F. infecter. See Fact.]
   [1913 Webster]
   1. To taint with morbid matter or any pestilential or noxious
      substance or effluvium by which disease is produced; as,
      to infect a lancet; to infect an apartment.
      [1913 Webster]

   2. To affect with infectious disease; to communicate
      infection to; as, infected with the plague.
      [1913 Webster]

            Them that were left alive being infected with this
            disease.                              --Sir T.
                                                  North.
      [1913 Webster]

   3. To communicate to or affect with, as qualities or
      emotions, esp. bad qualities; to corrupt; to contaminate;
      to taint by the communication of anything noxious or
      pernicious. --Cowper.
      [1913 Webster]

            Infected Ston's daughters with like heat. --Milton.
      [1913 Webster]

   4. (Law) To contaminate with illegality or to expose to
      penalty.

   Syn: To poison; vitiate; pollute; defile.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Infect \In*fect"\, a. [L. infectus: cf. F. infect. See Infect,
   v. t.]
   Infected. Cf. Enfect. [Obs.] --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

infect
    v 1: communicate a disease to; "Your children have infected you
         with this head cold"
    2: contaminate with a disease or microorganism [syn: infect,
       taint] [ant: disinfect]
    3: corrupt with ideas or an ideology; "society was infected by
       racism"
    4: affect in a contagious way; "His laughter infects everyone
       who is in the same room"