Howdy-doing is an informal greeting used in certain parts of the world including the United States and Canada. There are several synonyms or alternatives to howdy-doing that you can use to greet someone in a friendly or casual way. These include phrases like hey, hi there, what's up, how's it going, howdy, and what's happening. These phrases have a similar meaning and tone as howdy-doing and are suitable for both formal and informal settings. So next time you want to greet someone with a casual yet friendly greeting, consider using one of these common synonyms.