M/M
M/M drawing by Franco.
M/M is an abbreviation used in spanking art to signify an artwork or story that features an adult male spanker and an adult male spankee.
It could be, for example, a historic master/servant, prison officer/inmate, or similar scene. Besides spanking for discipline, adult spankings in art and literature are also often erotic spankings in sexual scenes. In the case of M/M, these might be gay.
M/M is man spanking art.