means A long, narrow cut or opening, or the act of making one with a sharp edge.

from From Old English 'slitan,' to tear or cut, with cousins across the Germanic family — Old Norse 'slíta,' Old High German 'slizan' — all carrying the sense of rending or splitting apart. The deep ancestor is a Proto-Germanic root meaning 'to split,' and you can hear its violence preserved in the word still: it is a noun born from a verb that does damage.