The word "mountainously" refers to something that is full of mountains, or that presents the characteristics of a mountain in its size, height or steepness. Some synonyms for "mountainously" could be "hilly", "rocky", "elevated", "towering", "massive", "lofty", "jagged", "rugged", "precipitous", "steep", "austere", "barren", "wild", "imposing", "majestic", "gigantic", "enormous" or "monumental". All these words convey a sense of grandeur, strength and power, as well as a certain degree of harshness and difficulty. Using synonyms can help to enrich your language and create more vivid and precise descriptions.