You've got big plans. Huge plans. Whatever it is, it's going to blow minds and absolutely rock worlds! Well, to some people those plans might sound a bit grandiose, or unnecessarily overblown and even highfalutin.
Coming from the Italian word grandioso (meaning "grand" or "noble"), the adjective grandiose is kind of like Italian hand gestures: big, exaggerated, and over the top. And it's that excessiveness that pushes something grand (large, with an air of distinction) into grandiose (large, but trying too hard) territory.