A shower was a device that cleansed the user with a stream of water.
When her Games class at Coal Hill School was called off due to frozen pipes disabling the showers, Susan Foreman played Snakes and ladders while her classmates listened to music and danced. (PROSE: Time and Relative)
There were ultrasonic showers in the TARDIS, (PROSE: The Empire of Glass) "with a control panel that would confuse a Jumbo Jet pilot". Ace could never figure out how to use them, so instead, she washed herself in the sink and used plenty of deodorant. (PROSE: Echo)