What's the largest open-source dictionary that includes brief definitions of each word? Wiktionary is a great resource but:
There are over 200K words in the scowl list that aren't in wiktionary. I'd use scowl directly, but it only list words and has no definitions.
Wiktionary intentionally includes misspellings (sometimes not marked as such, and sometimes as redirection), and I'm looking for only correctly-spelled words.
Wiktionary's definitions are often lengthy, not brief.
It's difficult to automatically extract the portion of a wiktionary page that's the definition.
I'm somewhat surprised this question isn't in the FAQ, and that I couldn't find the answer by searching this site.