It happens to the best of us. We like the big words, and we throw them out there just to seem all awesome and then we're corrected and instead look like big fat vocabulary-posers. Here's a quick list with pronunciation guide so that you don't look like an ass.
1) Behemoth - It's not just big, it's really, really big. So it's be-HEE-mith
2) Anathema - As in, I really, really hate you. Big time. a-NATH-eh-ma (NATH like "math")
3) Simpatico - As in, I really, really like you. We think the same. sim-PAT-eh-ko
4) Allegory - As in, that's really, really not what the story is about. You'd think in my college education as a religion major I'd be able to use this one about symbolism in literature correctly. Just so you know it's AL-a-gory
5) Tepid - It's not hot, it's not cold. It's really room temperature. Also doesn't sound anything like a Native American lodging. T-EH-pid