A statistic in baseball that compares the number of Ground Outs (ground ball hits that lead to an out for the batter) to Air Outs (fly balls that lead to an out for the batter), which determines the mix of fielded out types for both batters and pitchers. For each Ground Out (GO) and Air Out (AO), both the batter put out and the pitcher on the play receive either a GO or AO on their stat line, which is used in the calculation of the ratio.
Also referred to as "Ground Ball Fly Ball Ratio (G/F)" or "Ground Outs Per Fly Out/Air Out".
For batters, this ratio will show the number of times a batter grounds out to the number of times they fly out or air out. For example, if a batter has a GO/AO of 2.5, they were put out 5 times by ground out for every 2 times they are put out by air outs or fly outs. This suggests that the batter is much more likely to hit ground balls than fly balls compared to a batter with a low GO/AO.
This is the same for pitchers where the ratio compares the number of times their pitches lead to ground outs compared to air outs or fly outs. For example, if a pitcher has a GO/AO of 0.25 they generate 4 air outs or fly outs to every 1 ground out, which suggests they are the type of pitcher that sees more fly balls hit off of them.