A food originating in the Modenese Appennines; plural form is ciacci.
The ciaccio is prepared by cooking some leavend dough between two specially shaped iron tools (the cotte: they resemble a circle with a long handle) greased with a piece of lard. The dough can be either prepared with regular flour, in which case you have the savory ciaccio, or with chestnut flour - the sweet ciaccio.

While the sweet ciaccio is eaten accompanied with honey or jam, the savory ciaccio is served hot, brushed with a spread composed of pork lard, garlic and rosemary. It is very good either way - at least, in this noder's opinion.

The ciaccio is a close cousin of tigella and borlengo: even in appearence, it looks like a compromise between them: while considerably larger and thinner than a tigella it is much thicker and smaller than the borlengo. It is considerably much harder to find than its siblings though, as it is is almost exclusively prepared by somewhat remote mountain restaurants.