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Causes the target's ability to be rendered ineffective as long as it remains active. If the target uses Baton Pass, the replacement will remain under this effect. Fails if the target's ability is Multitype. Pokemon protected by Magic Coat or the ability Magic Bounce are unaffected and instead redirect this move back to the user.
Gastro Acid is not a common sight in competitive matches, even though the effect can be really useful to keep in check Pokemon that depend solely on their abilities to be threats. If you need a way to negate the foe's ability, Mold Breaker is typically superior despite the less distribution as it does not require both a moveslot and a turn to work.
Theoretically, in doubles or triples battles if you pair it with a Pokemon that the only neutering thing is its own ability (such as Truant for Slaking), then it would be a decent strategy. On the other hand, it's one-time-use and requires the surprise factor to work.