How to add synonym dictionary to mysql FULLTEXT search?

Question

That way if I search for the term "mens" the term "gentlemen" will match.

I tried this:

SELECT * 
FROM cart_product
WHERE MATCH (
product_name, product_description, product_brand, metal_type, primary_stone, product_type, product_type_sub, product_series, primary_stone_sub
)
AGAINST (
'THESAURUS "english" EXPAND SYNONYM TERM OF "gentlemen"'
)

But that doesn't seem to work. Is this wrong? is there somethig else I have to do with this?