Wordpress as thesaurus/dictionnary: what approach?

Question

I'm willing to develop a thesaurus/dictionary for the Berber language. A website that allows comunity members to add new words/synonyms/antonyms..

1. How to relate words (posts) to each other? by using tags? but with this approach, it's hard to keep organization when posts names/slugs are modified; then tags should be updated too.. consider the word "big" is already inserted as a post, then someone added the word "large" and related it to the word "big" by inserting a tag on it.. then comes a 3rd user and added the word "great"; this means all the posts with similar synonyms should be updated! isn't it a bad approach going the tags way?
2. Another issue is when I want to add antonyms; I cannot add them as tags since tags are reserved for synonyms! so how to solve this complex structure keeping everything easy to maintain?

Update

Why taxonomies won't work? Because taxonomies are meant for categorizing things that have different characterestics from each other; like in a movie database, you have a taxonomy for actors, one for diretors for example.. But since the words in a dictionary are "equal" they should be treated the same.. so I think more on using custom fields..

Thanks for any help and sorry for the long post :)

PS; I don't want to use plugins to avoid dependence problemes.