In cricket terminology, what does ‘walking’ mean?

In cricket terminology, what does ‘walking’ mean?

This refers to the occurrence of a batsman, walking off the pitch, knowing or believing that he is out, rather than waiting for an umpire to give him out (giving up the chance that the umpire may give benefit of the doubt regarding a dismissal if he is not certain that the batsman is out). Walking is generally considered to be sporting behaviour, but is becoming increasingly rare in international cricket; Adam Gilchrist of Australia has declared himself a “walker”.