From Armagetron

Digging, or a Pure Grind is a skill in which a player goes directly into another players tail or a wall of the arena, goes just until they are almost out of rubber, then they turn. This makes it harder for other players to get get behind that wall—to "beat your grind." When you get experienced at it, you can come up with variations that can make it nearly impossible for someone to get through.

Note: Until recently, this was known exclusively as a "pure grind"--and is still known as such by older players--but newer generations of players have felt compelled to come up with all new terms.