It doesn't help with stuff found in the wild, but if you're working from a text most math books will either list all symbols at the beginning of the index with references to where the notation is introduced and defined, or they have a separate symbol index or glossary of notation.
If you can find it.
But there is no way to look up any given dumb-ass notation, or even to know how to pronounce it. Most notations are used to mean a dozen different things, so you can't even be sure, if you read about it, you are reading about the right one, if you do find it. And if you find the right one, it still won't say how to pronounce it, so you can't even ask without sounding like a dummy.
It is all very insular. Or, maybe, was, before Youtube.