Source : Webster's Revised Unabridged Dictionary (1913)

Tickler \Tic"kler\, n.
   1. One who, or that which, tickles.

   2. Something puzzling or difficult.

   3. A book containing a memorandum of notes and debts arranged
      in the order of their maturity. [Com. Cant, U. S.]
      --Bartlett.

   4. A prong used by coopers to extract bungs from casks.
      [Eng.]

Source : WordNet®

tickler
     n : a file of memoranda or notices that remind of things to be
         done [syn: {tickler file}]