A Vulcan master or Kolinahr master was a religious position on the planet Vulcan similar to a monk.
Vulcan teenagers went to Vulcan masters to learn the ways of logic and how to suppress emotion. For example, Tuvok was sent to study under a Vulcan master when he was a teenager and had rebelled against Vulcan discipline. (VOY: "Gravity")
In 2368, Tuvok bought a meditation lamp from a Vulcan master, who charged double the price when he saw the Starfleet insignia of Tuvok and Kathryn Janeway. (VOY: "The Gift")
Tom Paris condescendingly described Tuvok as "the Vulcan master" in 2374, and relished Harry Kim "putting him down a peg." (VOY: "Demon")
In 2376, Tuvok recalled witnessing a Vulcan master perform a variation of the mind meld, known as the "Bridging of Minds". (VOY: "Unimatrix Zero")
Vulcan masters also preside over kolinahr when a Vulcan wishes to purge him or herself of all emotion. (Star Trek: The Motion Picture) T'Klaas, a student of Surak, was one of the first kohlinar masters. (ENT: "Awakening")