When you give the definition of a word, you define it, but what(if there is) is the word for giving a synonym of a word?
The term is to synonymize , but it is not a common expression. You can say to provide a synonym/synonyms:
- To analyze or provide the synonyms of (a word or taxon).
(American Heritage® Dictionary)
- (Linguistics) (tr) to analyse the synonyms of or provide with synonyms.