Commonly recognized examples of confined spaces include transformer vaults and manholes. But we don't declare something a confined space only if it's on a list of recognized examples. A space is "confined" if getting in or out of it is difficult, or the space isn't meant for continuous occupancy. By the OSHA definition, both conditions must be met. Should this be your definition?

If you just want to see what you can legally get by with, the OSHA definition is adequate. If you want to identify hazards and protect yourself from them, then a space is confined if either condition is met.

An equipment vault may be easy to enter and exit. Just go through the door. Is that vault "confined" or not? A shallow pit is easy to enter and exit. You don't even have to bother with a door. While you're lying on your belly adjusting the sump pump level float, accumulated carbon dioxide kills you. Should you have pulled a confined space permit?