Thesaurus.com Search Shortcut — James

This add-on adds Thesaurus.com to the list of search engine shortcuts in Firefox.

By typing "thes" followed by a space, you are then able to search for synonyms on Thesaurus.com.
For example, after typing in the query "thes fire" your tab will redirect you to search results showing synonyms for fire on Thesaurus.com.
You can modify the keyword for this extension by going to the Firefox Options -> Search -> Search Shortcuts