What does "slitting" mean?

Slitting: from Slit. Slitting file. See Illust. (i) of File. -- Slitting mill. (a) A mill where iron bars or plates are slit into narrow strips, as nail rods, and the like. (b) A machine used by lapidaries for slicing stones, usually by means of a revolving disk, called a slicer, supplied with diamond powder. -- Slitting roller, one of a pair of rollers furnished with ribs entering between similar ribs in the other roller, and cutting like shears, -- used in slitting metals.