I agree that traditionally "living beyond one's means" referred to buy now, pay later and basic economic principles.
However, I would like to expand this question (and response) to the root of the cause of what we typically refer to as "living beyond one's means".
It really comes from a culture (society) that is conditioned to consume, compete, rather than collaborate, replenish, etc. Fortunately, this "trance" that western society has been under is shifting. We only hope it's not too late. I would encourage you to look at this from a broader perspective that just economic principles and approach it from a perspective that includes:
one's global footprint: (to understand "living beyond one's means" in a much larger context)
the concept of the Commons
Paul Hawken 's Ecology of Commerce and Natural Capitalism are excellent resources to begin with.
Other resources cited below:
Typically, people who rely heavily on credit cards or other forms of credit are said to be "living beyond their means." In an average week, I expect to receive 3-5 offers for a "pre-approved" credit card. Society is bombarded by offers to "buy now, pay later." Sometimes, the desire to buy more is stronger than the desire to remain debt-free. Some kinds of debt are considered "good" debt (ie a mortgage), while other kinds of debt are not good debt (credit cards). Basic economic principles show that you must have more money coming in than going out. Usually, this is where credit cards become an issue. As a result, interest rates (money you pay someone in addition to the money you borrow) go up, and payments go up. As a whole, our nation is relying heavily on bad forms of debt and are currently in a deficit.