Permafrost is an underground layer of soil and bedrock that remains frozen all year round. When we use the word "permafrosted," we are referring to something that has been affected by this icy environment. There are several synonyms that can be used in place of "permafrosted". Some of these include frozen, frosty, icy, cold, and frigid. Other options include Arctic, glacial, polar, and sub-zero. No matter what synonym you choose to use, it will help you to convey the idea of something being frozen solid and affected by the harsh conditions of permafrost.