To overstuff means to pack something so full that it can barely hold everything inside. When you overstuff a backpack, you cram in so many books and supplies that the zippers strain and the fabric bulges. A cook might overstuff a turkey, pushing in more bread stuffing than it can comfortably hold.

The word suggests going beyond what's reasonable or comfortable. An overstuffed suitcase might be impossible to close without sitting on it, and an overstuffed sandwich has so many ingredients that they tumble out with every bite. Furniture like chairs and sofas can be overstuffed too, meaning they're packed with extra padding to make them soft and plump.

Overstuffing usually creates problems. That overstuffed backpack becomes heavy and uncomfortable to carry, and the overstuffed turkey might not cook evenly.