A ship-launched subspace weapon that tears open the fabric of space, banned under the Second Khitomer Accords but used by the Son'a in 2375 and carried by Vadic's warship Shrike in 2401.
An isolytic burst is a subspace weapon. When it detonates it rips a tear in subspace that is unpredictable and is drawn towards active warp cores, which is why such weapons were outlawed by the Second Khitomer Accords.
In the film Star Trek: Insurrection, a Son'a battle cruiser fires one at the Enterprise-E in the Briar Patch. With the tear closing on the ship, Geordi La Forge ejects the warp core and detonates it to seal the rift.
In the Picard episode Disengage, the Titan's crew find that the Shrike, commanded by Vadic, carries dozens of isolytic burst warheads among its arsenal. A related device, the isolytic weapon built by Ruon Tarka to destroy the Dark Matter Anomaly, drives much of Discovery's fourth season.