Is there a tool to learn to pronounce aviation jargon accurately?
With the exception of abbreviations (like FSDO, pronounced fizz dough) there's not much "jargon" in aviation that's not a standard word in whatever language you're speaking. Words like "dihedral", "anhedral", "aileron", etc. should certainly show up in a dictionary.

The abbreviations are "tribal knowledge" the same way they are in any other field (e.g. SCSI, SATA, IMAP in the tech field). I'm not aware of any authoritative compendium of pronunciations.