From meaning to word
A standard dictionary maps a word to its meaning; a reverse dictionary maps a meaning to a word. By analysing your description against a huge base of definitions and related terms, it surfaces the words that best capture the idea you are trying to name โ even when you cannot remember the word at all.
The more precise your description, the better the results. A clear phrase like 'a feeling of great happiness' returns focused matches such as joy, elation and bliss, while a vaguer input casts a wider net. Either way, the words are ranked so the closest fits come first.