The Collaborative International Dictionary of English v.0.48:

Spending \Spend"ing\, n.
   The act of expending; expenditure.
   [1913 Webster]

   Spending money, money set apart for extra (not necessary)
      personal expenses; pocket money. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

spending money
    n 1: cash for day-to-day spending on incidental expenses [syn:
         pocket money, pin money, spending money]