"Signation" does not appear to be a commonly used word; therefore, there are limited synonyms available. However, some possible substitutes for "signation" could be "signature" or "signing." These terms indicate the act of signing one's name or indicating agreement or authority through a signature. Another option might be "marking," which refers to making a symbol, signature or indication on a document or object. Alternatively, "sealing" could also be used to indicate the approval or authorization of a document or agreement. While "signation" may not have many synonyms available, there are numerous other ways to express the same idea depending on the context and intended meaning.