Dreadnought

A Dreadnaught is a type of Cardassian interstellar cruise missile. The Cardassians used them to attack Maquis worlds. One was captured and reprogrammed by B'Elanna Torres . We see her thought processes at work with this device. She used large quantities of advanced technology in a machine designed to blow up. The Dreadnaught was directed it to attack a Cardassian world, when it was brought to the Delta Quadrant. It proceeded towards a nearby planet that somewhat resembled its assigned target. The crew of the USS Voyager managed to destroy it, but were greatly hampered by its onboard defenses. This included a paranoid array of "what if" instructions to keep it from being defused if it were intercepted.

Since a Dreadnaught missile has no crew, it isn't technically a starship, although it does have it's own defensive weapons to prevent interception. The Cardassians may have used them to attack Maquis targets in the DMZ without openly violating their treaty commitments.