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)
While trying to escape from Ashbridge Cottage Hospital, the Third Doctor hid in a shower. (TV: Spearhead from Space)
Roche's TARDIS disguised itself as a shower cubicle and an ice cream van before he disposed of it as part of a plan to trap the Furies that were hunting him. (PROSE: The Suns of Caresh)
Ian Chesterton had in the shower at a hotel in Illinois. (PROSE: The Mother Road)
On the second day he was staying at Craig Owens's house, the Eleventh Doctor sang opera in the shower while Craig impatiently waited in the hallway for his turn. (TV: The Lodger)
Clara Oswald got into an argument with the TARDIS after it played a practical joke on her in the shower by relocating her bedroom. (HOMEVID: Clara and the TARDIS)