pin moneyˈpin ˌmoney noun [uncountable] 
British English a small amount of extra money which someone earns to spend on things which they want but do not really need: 
She helped her uncle out sometimes just to earn a bit of pin money.
British English a small amount of extra money which someone earns to spend on things which they want but do not really need: She helped her uncle out sometimes just to earn a bit of pin money.