Balunbalunan is the Filipino term for "Gizzard". Gizzard is a muscular part of the fowl  behind the lower stomach. It is a tough part , so it takes a lot of time before it is cooked properly and tender. Before cooking, it has to be cleaned thoroughly and properly  as the they contain the ingested grits/food of the fowl

In Philippine Cuisine, the Gizzard is used as ingredients for or made into for various dishes, such as  Adobo  and a street food of marinated and grilled , Balunbalunan on skewers called Inihaw na Balunbalunan (see related Article).

Balunbalunan is also spelled Balumbalunan or Balun-Balunan. 

Below is a picture of thoroughly cleaned Balunbalunan for marinating and grilling.