A bathroom fitting on Starfleet ships that cleans the body with sonic vibrations instead of water, standard in crew quarters from the 2270s onward.
The sonic shower is first seen in Star Trek: The Motion Picture. After the navigator Ilia is taken by V'Ger, a mechanical copy of her appears inside the sonic shower in her quarters aboard the refitted Enterprise, and it is there that Kirk and Spock first question the probe.
The fitting is mentioned regularly in later series as a normal part of life aboard ship. Characters in The Next Generation, Deep Space Nine and Voyager speak of taking or needing a sonic shower.
The unit works by vibrating dirt loose from the skin and clothing. It does away with the need to carry and recycle large quantities of water for washing on long voyages.