Ceiling

Assuming you’re inside a building, you can see the most literal example of a ceiling by looking up (feel free to do so now...if you are outside, you might have to wait until later).

Financially speaking though, this usually refers to the top-most level that can be tolerated, or is desired, or can be imagined. For instance, the debt ceiling we often hear politicians talking about is the maximum amount of debt that the country is legally allowed to borrow (until they raise the ceiling). As of summer 2018, debt ceiling is $20.46 trillion (yep, trillion), which means that Congress has approved borrowing up to that amount.

To take it out of the -illion range and into finances we're all probably more familar with: You’re car shopping. You have a budget of what you can spend. There's a ceiling on the price you can afford. That's the max amount you can borrow and still make payments comfortably.