Bernstein's reverse dictionary, Bernstein T.M., Grambs D., 1988.
A conventional dictionary lists words alphabetically and gives you their meanings. This unconventional dictionary lists an array of meanings alphabetically and gives you the words. That is why it is called a Reverse Dictionary.
The words it discovers for you are those you have momentarily forgotten or those you never knew or those of whose meanings you were not quite certain. If I tell you how the concept originated, it may make the idea more quickly understandable.