If your written language consists of pictures rather than letters and words, your written communication would be hieroglyphic in nature. Ancient Egyptian writing was hieroglyphic.
The pictures that make up hieroglyphic language are called hieroglyphs. The word descended from the Greek hierogluphikos which could be translated to mean "sacred carvings." Back when written communication was literally carved in stone, most of what was written was important, or "sacred." Today if someone describes your handwriting as hieroglyphic, they mean something quite different - your writing is awful and illegible.