The Collaborative International Dictionary of English v.0.48:

Blotter \Blot"ter\ (bl[o^]t"t[~e]r), n.
   1. One who, or that which, blots; esp. a device for absorbing
      superfluous ink.
      [1913 Webster]

   2. (Com.) A wastebook, in which entries of transactions are
      made as they take place.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blotter
    n 1: absorbent paper used to dry ink [syn: blotting paper,
         blotter]
    2: the daily written record of events (as arrests) in a police
       station [syn: blotter, day book, police blotter, rap
       sheet, charge sheet]