, eddwo wrote

A ~100,000 word dictionary shouldn't come in at much more than about 5MB even in an indexed database file

5MB over 100,000 words gives 52 bytes per word. Fine for a word-list, but a dictionary tends to carry the word, pronunciation key, definition, inflections, declensions, synonyms, and possibly an etymology - for that you're easily looking at at least a few hundred characters per entry.

The OED, for example, has 600,000 words.