I'm American.  My husband and I are middle class, maybe upper middle class, at least I think we are.  My husband is the sole wage earner, and he doesn't necessarily make a huge amount of money, but we are smart with what he earns. My husband and I are retirement age but he's not ready to retire yet.

 I've never really thought about an *official* definition of the term, but to me it means: we do not run low on money before the next payday; we are able to pay our bills without struggle; we are able to have a healthy savings account; we are able to contribute to 401k and IRAs; we own our home outright; we were able to save money to put down fifty percent on a car and were able to pay off the remainder in eighteen months; we can vacation *within reason* without breaking the bank; we can afford to eat out if we want to; we do not need to use credit cards ever. The fidiciary who handles our investments tells us we're in the top ten percent of HIS clients as far as retirement savings/investments.  That is scary to me because it means a whole lot of people are not going to be able to retire without being a burden on society, or they'll have to work well beyond retirement age and keep younger people out of the workforce.

To me, working class people live from paycheck to paycheck and any expenses above the ordinary can cause hardship.  

Upper class to me is people who are able to make huge purchases without checking their accounts...like writing out a $80k check for a car.  Vacations are yearly European destinations, or they own vacation homes.