Short for Master/slave. An extreme form of D/s relationship where the slave voluntarily gives up all personal freedom to the Master or Mistress (or both).The creation of such a relationship is often marked by the giving and accepting of a collar and sometimes by the signing of pseudo-legal ownership documents.
She asked to be set free from their M/s agreement. He has said she can go as long as she finds him a new slave first.
by Tesseract June 20, 2005