Retirement was the action of ceasing to work in a professional capacity, or the state of having done so.
The Doctor Edit
Following the loss of Amy Pond and Rory Williams, (TV: The Angels Take Manhattan) the Eleventh Doctor retired from his travels to Victorian London, secluding himself in his TARDIS for a lengthy period of time. (TV: The Snowmen, The Great Detective) He eventually returned to action after being phoned by Clara Oswald. (TV: The Bells of Saint John)
Later, the Eleventh Doctor voiced at the National Gallery his hope that he could retire one day and become the curator of it. Immediately after, he was met by the Curator himself, who implied that the Doctor would indeed become him one day. (TV: The Day of the Doctor)
The Twelfth Doctor promised Nardole to semi-retire from leaving Earth to guard the vault at St Luke's University. Upon meeting Bill Potts though, he struggled to keep this promise. (TV: The Pilot) He eventually broke it completely. (TV: Oxygen, World Enough and Time)