The toilet, also referred to by the Ferengi as a waste extraction fixture, is a device used for the disposal of bodily wastes. The waste extraction system was the system used to manage and process that and all other related wastes.
During the first mission of the starship Enterprise NX-01, Captain Jonathan Archer declared that the Vulcan High Command didn't think Humans could flush a toilet without a Vulcan to assist. (ENT: "Broken Bow")
In 2151, Worley Elementary School in Kenmare, County Kerry, Ireland on Earth, sent questions, letters, and drawings to the Enterprise. One question asked was "When you flush the toilet, where does it go?" and one of the few that was answered personally – Captain Archer delegated it to chief engineer Trip Tucker. Commander Tucker was not pleased with the captain's selection of questions for him and protested, but ultimately relented and explained to Molly the ship's processes of recycling and biomatter resequencing. (ENT: "Breaking the Ice")
The brig aboard Starfleet ships included facilities such as a sink and toilet, which were enclosed behind the wall until needed. A sign above the toilet read "do not use while in spacedock." (Star Trek V: The Final Frontier)
Waste extraction points on a Bajoran transport are located in individual quarters. After Ibudan was murdered in 2369, Dr. Julian Bashir located seofurane fragments near the waste extraction point in Ibudan's quarters on the transport. (DS9: "A Man Alone")
It was said that the waste extraction fixtures at the Nagal Residence on Ferenginar were plated with latinum. Quark, believing that he was about to become the next Grand Nagus, said that the first thing he was going to rip out the plated fixtures and replace them with solid latinum fixtures. (DS9: "Body Parts", "The Dogs of War")