Magnetometric guided charge

From Memory Alpha, the free Star Trek reference.

The magnetometric guided charge is a projectile weapon employed by the Borg, capable of auto-acquiring a metallic target under conditions in which sensors are ineffective. In 2367, a Borg cube forced the USS Enterprise-D from its hiding place inside the Paulson Nebula by firing magnetometric guided charges into the cloud. (TNG: "The Best of Both Worlds")