Don't get me started

...
To my knowledge, the ISU itself has never used the term "Senior B."
Over the past couple of years, I have requested an exact official definition many times on GS -- in many different threads.
Never got a direct answer containing an exact official definition, although people have posted replies that indirectly addressed my question.
That said, the ISU does refer to "senior international events." So I have concluded that "senior international events" that appear on the official ISU calendar (the overall ISU calendar, not the Challenger-specific calendar) are what people (outside the ISU) commonly refer to as Senior Bs.
And the ISU calendar includes many senior internationals other than Challenger events.
Coupe de Nice is a classic example of a Senior B that is not a Challenger event.
Another example: Last year's Skate Canada Autumn Classic was a Challenger event. This year's will be just a "normal" Senior B.
Per ISU documents, World Standings points are higher for Challenger events than for other senior internationals. So the ISU does distinguish btwn Challenger events and other senior internationals.
Still would love to get an exact official definition of Senior B ....