A mummy was a corpse whose skin and dried flesh had been preserved through the process of mummification.
Many cultures, especially the Egyptians, deliberately preserved bodies of important persons as mummies. Circa 2650 BC, the First Doctor wrapped up the Monk as a mummy to get him out of the way. (TV: The Daleks' Master Plan) Osiran service robots resembled Egyptian mummies. (TV: Pyramids of Mars) Walking mummies were part of the Egyptian section of EarthWorld on New Jupiter. (PROSE: EarthWorld)
On a visit to the National Museum in London during the 1970s, the Third Doctor indicated an Egyptian mummy to Jo Grant, claiming that he knew the person in question in life. (AUDIO: The Doll of Death)
The Foretold was a mythical mummy who appeared only to those whom it was about to kill, which it did in exactly sixty-six seconds after appearing. The Twelfth Doctor revealed it to be a soldier, kept alive by ancient technology while waiting to be released from his duties, whose degeneration over time had given it the appearance of a mummy. (TV: Mummy on the Orient Express)