Anhydrously is a word used to describe something that is completely devoid of water. There are a few synonyms that can be used in its place, such as aridly, parchedly, and desiccatively. Aridly can be used to describe a place that is dry and barren, while parchedly can be used to describe something that is so dry that it feels as if it could catch fire. Desiccatively can be used to describe something that is being dehydrated or dried out, much like an anhydrous substance. Other possible synonyms for anhydrously could include moisture-less, dewatered, and water-free.