"Signable" is a versatile term that implies the capability of being signed or marked with a signature. When searching for alternative words with similar meanings, one can consider terms such as "executable", which reflects the idea of a document or agreement being capable of being legally signed or enforced by the concerned parties. Additionally, one can use the word "signifiable" to convey the notion of something being able to be signed or denoted through a signature. Other possible synonyms include "signature-ready", "signatory" or "sign-worthy", all emphasizing the readiness or appropriateness of a document to be signed. Picking the right synonym will largely depend on the context and intended use.