Photo: Complexio / Getty Images Definition A nest egg is a significant sum of money an individual or family has saved or invested for a specific future goal. A nest egg is a significant sum of money an individual or family has saved or invested for a specific future goal. Typically, a nest egg is designated for longer-term savings goals such as retirement. In fact, saving for retirement is often referred to as “growing your nest egg.” Definition and Examples of a Nest Egg The term “nest egg”