Grandiloquent is a fancy term for, well, being fancy or pretentious. In fact, you might say grandiloquent is itself a pretty grandiloquent word.
The word grandiloquent generally refers to the way a person behaves or speaks. Politicians and schoolteachers are the usual suspects of this manner of behavior, known as grandiloquence, but it can refer to anything that's overbearing or pompous in style or manner. Architecture, especially, is highly guilty of being grandiloquent — if you check out just about anything built in the Baroque style, you could describe it as grandiloquent.