You can edit an existing thesaurus entry
On the Search tab, click Thesaurus.
Click the entry in the list.
If necessary, change the entry type.
If you change the entry from one-way to equivalent, then the existing search term automatically moves to the beginning of the synonyms list -- provided that it doesn’t already exist in the synonyms list.
If you change the entry from equivalent to one-way, the existing synonyms remain intact, and a blank Search Terms field appears.
Update a synonym by deleting it and re-entering it.
Click Save.