Dreadnought

A Dreadnaught is a type of Cardassian interstellar cruise missile. The Cardassians used them to attack Maquis worlds.

B'Elanna Torres reprogrammed one of these missiles when it was captured by the Maquis after failing to detonate. We see her thought processes at work with this device. She used large quantities of advanced technology in a machine designed to blow up. She directed the Dreadnaught 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.