OmniSets has had the ability to write 2 definitions, not just one, but using the format:

"definition" ;; "definition" for quite a long time now. I'm making the decision to remove this feature for basically 3 reasons:

1. Usability: A lot of people don't know how to use it, even after having help guides, etc. It's not simple to figure out when doing written response either.
2. Ease of development: It's not the most simple thing to have and causes more headaches when building more useful features.
3. Not enough use: I've not seen more than maybe more than a 100 cards use it, and even then it's just one per set.

I'm pretty sure I made a poll about this a while back and people said they only used it once. It won't be gone immediately, but you should probably stop using them.

That being said, I like the idea of them and with the new Intelligent Grading AI, it might be possible to bring the feature back in a much simpler way.