From time to time I have to forward our bug severity scale to a customer responsible for reporting bugs.
We use only the first five. I do not remember when I reported a bug with severity six or seven.
1. Showstopper - blocks development and/or testing work, production could not run
2. Critical - crashes, loss of data, major memory leaks
3. Major - major loss of function
4. Minor - minor loss of function; other problem where easy workaround exists
5. Trivial - cosmetic issue like typo, misaligned images, and similar
6. Fix if time - super-low priority
7. Don't Fix