A pension crisis is when retired people don't have enough money to live on or to do the things they want to do when they retire. This happens when the government or companies that someone works for have not put aside enough money for those people when they retire. Usually, the government or companies have promised money for when people retire but have not made enough contributions to meet these promises. This means that when people retire, there is less money for them than expected. In some cases, this can be very difficult for people and caused a crisis.