Definition - What does Reverse mean?
"Reverse" is the gear opposite of "forward." In auguring, the auger turns counterclockwise – as seen from the operator's position – when it is in the "reverse" gear. The auger turns clockwise when in the "forward" setting.
In reverse, the auger bit is moving backward in the bore toward the operator and the auger, just as an automobile moves backward when it's gearshift lever is placed in reverse and forward when it's gearshift lever is placed in one of the forward positions.
Trenchlesspedia explains Reverse
In other boring, "reverse" is used to back the bit out of the bore. When backing the bit out of the bore reverse is the gear used to pull tubing or pipe back through the bore.
The reverse gear is also used – in conjunction with the forward gear – to write the bit back and forth in a pilot bore, to enlarge the bore so that it will accept a pipe larger than the pilot bore.