The Collaborative International Dictionary of English v.0.48:

Spot \Spot\, v. t. [imp. & p. p. Spotted; p. pr. & vb. n.
   Spotting.]
   1. To make visible marks upon with some foreign matter; to
      discolor in or with spots; to stain; to cover with spots
      or figures; as, to spot a garment; to spot paper.
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   2. To mark or note so as to insure recognition; to recognize;
      to detect; as, to spot a criminal. [Cant]
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   3. To stain; to blemish; to taint; to disgrace; to tarnish,
      as reputation; to asperse.
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            My virgin life no spotted thoughts shall stain.
                                                  --Sir P.
                                                  Sidney.
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            If ever I shall close these eyes but once,
            May I live spotted for my perjury.    --Beau. & Fl.
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   To spot timber, to cut or chip it, in preparation for
      hewing.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spotting
    n 1: the act of spotting or staining something [syn: staining,
         spotting, maculation]
    2: the act of detecting something; catching sight of something
       [syn: detection, catching, espial, spying,
       spotting]