I've written about the importance of a good vocabulary... But sometimes people demonstrate their intelligence best by explaining things in the simplest of terms. Why use a long, complicated explanation, when a brief, simple one will work? This way, you get your point across without confusion.
Some might call this "dummy down" but I prefer to think of it as simplification. If someone doesn't understand you, or worse, gets bored... they're just going to tune out and ignore you anyway. Don't waste your time. Work on your communication skills and be clear.