Hi Sheila, and welcome to Chef Talk.
Heavy appetizers (or hearty appetizers) would mean hot or cold appetizers that would be enough for a meal: skewers of shrimp or meat; wings; small grilled lamb chops; rollups or wraps; meatballs; smoked salmon-- you get the picture. You'd be too full to have a regular meal if you tasted all of them!
Enjoy the board! Browse through all the forums and post according to whichever is the best forum for your question. We do ask that home cooks like you and I to consider the professional chefs' forums as "read-only".
Welcome!
Mezzaluna