A flat-bladed hand tool usually struck by a mallet to cut and shape wood.
There are numerous different shapes/types of chisel (e.g. bevel-edged and firmer styles which have flat sides, socketed or with a tang), in a range of widths from perhaps 1/8" (3mm) at narrowest to 2" (50mm) and more at the widest, as well as different sizes, with butt chisels for example being deliberately shortened both in the blade and sometimes also the handle.