[kccqzy]

I have memories of using the Dictionary Development Kit to create custom dictionaries (I remember creating one for medical jargon) about ten years ago. (At that time custom dictionaries are placed in ~/Library/Dictionaries, and system dictionaries in /System/Library/Dictionaries, not some obfuscated path like now.)

To find the Kit in question, simply Google "com.apple.TrieAccessMethod" and you should find it online.