In cricket, a batsman is not out if they come out to bat in an innings and have not been dismissed by the end of an innings. The batter is also not out while their innings is still in progress.

What means not out?

: not dismissed (as after an opponent's unsuccessful appeal to an umpire) : with innings uncompleted (as at the end of a day's play) not-out. noun.

What does not out do to average?

Batting averages are personal and are calculated as runs divided by dismissals, so a player who often ends the innings not out may get an inflated batting average, on the face of it.