Is there an actual (absolute) definition of a "mild winter?"

I keep seeing advice that such and such is possible to do if you have "mild winters."

This isn't about my USDA zone or expected expected frost dates.

I grew up in sunny California with essentially no frost date, although we did still experience brief early morning freezes for a day or two, once every five or six years. I know that is considered a mild climate/having mild winters.

Now I live in a climate with actual seasons: frosts, freezes, snow, etc. Some winters are warmer than others, and I would call those a "mild winter," but that is only relative to the typical winter here. The conditions would still be fatal for much of a San Francisco Bay Area garden. On the other hand, my typical January-February is probably picnic weather for an Alaskan or other high latitude garden in the same timeframe.

Is there any specific definition of a "mild winter" that isn't based on a comparison to other places or other years in the same place?