Use Google and type in the appropriate word plus "definition". I have found quite a few definitions that way. Just be careful to pick and choose carefully, because some of the definitions aren't very scriptural.
there's a nifty little book called "Pocket Dictionary of Theological Terms", by Stanley Grenz (awesome), David Guretzki (one of my former profs ;) and Cherith Fee Nordling. It's just a little book and doesn't cost much, and contains definitions of around 300 terms and phrases. Check it out!