let say you came across a new word that you don't know the meaning of. first thing that you'll probably do is ask a friend (if one is with in the vicinity). If not you wait until you get home pick a dictionary or go online and look for the meaning of the word.
now what if you have a definition of a word in mind but can't remember the actual word for it? what do you do? of course you can always ask a friend for the exact word. but what if he doesn't know. you certainly can't go home, pick up the dictionary and go trough each word to find the right word. what you can do is go to the closest word that matches your definition and substitute it with that word, sub-standard it may be.
so what i'm proposing is, if it is not done already, is a reverse dictionary where you'd type in your definition and the word you're looking for pops out. genius right?
(or you could just probably grab a thesaurus or go online and google the word. hehe. :P)