This is really a two part question. How do you find a word that you forget, but you remember its definition? I have this problem routinely. I usually try googling "word that means fill-in-words-from-the-definition-here. But that doesn't always work.
For example, there is a word which means circular reasoning. What is it? I tried googling (that is, searching) word meaning circular reasoning, with no luck (on the first page of results). Same results at Bing. I also looked up "circular reasoning" on dictionary.com. That site had a definition, but no synonyms.
I know for a fact the word I'm looking for exists (I've seen it). You'd think Google could find it. I thought the word was tautology, but it seems to have a slightly different definition.
P.S. Example: So-and-so, on Fox News is a right-wing partisan (am I displaying my bias here?).
How do you know?
Because they're on Fox News.