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Stealth Rock can be removed by Rapid Spin.
Rapid Spin is a physical, normal type move that serves no other purpose at all in the metagame, and is worthless for anything but clearing stealth rock.
Because Rapid Spin is a normal move, ghost type pokemon exist, known as Spinblockers, which negate rapid spin's ability to remove sneaky pebbles, and spinblockers are often built solely to kill potential rapid spinners so that they can never get rid of stealth rocks.
However, some rapid spinners learn the move "foresight" which will let them hit a ghost type with rapid spin if they foresight as the ghost switches in. Negating one of the spinner's moveslots and making him more easily killable by the spinblocker is a welcome trade if it lets him get off a rapid spin to remove sneaky pebbles.
For this reason, some teams use two ghost type pokemon, so that one that gets foresighted can switch out safely to the other, who would still negate rapid spin and still beat rapid spinners, and can also switch out if he gets foresighted as well.
Countering (dual ghosts) the opponent's counter (foresight) to your counter (spinblockers) to their counter (rapid spin) to stealth rocks is a legitimate strategy in Gen V meta. Hopefully defog will help, but it's not likely since everything that gets it sans mew is flying anyway.
