Visuwords™ uses Princeton University’s Word Net, an opensource database built by University students and language researchers.
Note that this thesaurus is not in any way affiliated with Urban Dictionary.
Due to the way the algorithm works, the thesaurus gives you mostly related slang words, rather than exact synonyms.
To use the applet you only need to type a word into the search query at the top of the page and press 'Enter'.
A network of nodes or 'synsets' will spring out from the word that you entered.
It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.