A Wu Hsan (or woozie) was the Starfleet term for self-transporting artillery shells during the 24th century. The name was derived from the name of the Federation scientists who helped develop transporter technology in the 22nd century.
The shell used a sophisticated sensors and a microtransporter system. The shell then beams itself to a target within 40,000km and denotes. (The Dominion War Sourcebook: The Fires of Armageddon)