muscle, or cheaper cuts of beef
Muscolo di manzo sometimes appears on menus for the tougher, shoulder cuts of beef or veal, as muscolo di manzo con cipolle (braised with onions). It's also the cut of meat used for bollito or spezzatino.
There's also an organic vegetarian meat substitute made from durum wheat, called muscolo di grano, similar to seitan.
The plural, muscoli, is the Ligurian word for mussels.