D defs.my
Entry 4 senses Webster, 1913

Tickler

· Tic·kler · IPA /ˈtɪkələ(ɹ)/
01 n. One who, or that which, tickles.
  1. 1.
    One who, or that which, tickles.
  2. 2.
    Something puzzling or difficult.
  3. 3.
    A book containing a memorandum of notes and debts arranged in the order of their maturity.[Com. Cant, U. S.]
  4. 4.
    A prong used by coopers to extract bungs from casks.[Eng.]