"Waddy" is a term used primarily in Australian English, and is typically used to refer to a heavy wooden stick or club used as a weapon or tool. However, there are plenty of other words that could be used as synonyms depending on the context. These might include "billyclub," "cudgel," "crowbar," "hammer," "mallet," "sap," "sledgehammer," or "truncheon." The word "waddy" might also be used in a more colloquial sense to refer to a person who is tough or intimidating, in which case synonyms might include "bully," "brute," "ruffian," "thug," or "hooligan".