"Barkbound" refers to animals or plants that have a rough, bark-like exterior. However, there are many synonyms that can be used instead of this term. For example, "scaly" is a great replacement, implying the same rough texture. Other synonyms include "rind-covered," "crusty," and "encrusted." Additionally, "gnarled" can be used when referring to bark that is twisted and knotty. "Fibrous" is another option which denotes a texture made of a series of small, stringy strands. In any case, all of these synonyms can be interchanged with "barkbound" to add variety and vividness to one's writing, keeping it interesting for the reader.