A cyberneticist was a scientist who specializes in cybernetic lifeforms.
In 2366, Romulan Admiral Alidar Jarok admitted to lieutenant commander Data that he knew of a host of cyberneticists who would love to get their hands on him. (TNG: "The Defector")
Doctor Noonian Soong was a noted cyberneticist who was responsible for the construction of Data. When the two met in 2367, Data inquired of Soong as to which vocation he should have chosen to have met with Soong's approval, to which Soong replied that he had hoped that Data might have followed in his footsteps and become a cyberneticist. (TNG: "Brothers")
Commander Bruce Maddox worked at the Cybernetics Division of the Daystrom Institute in 2367. (TNG: "Data's Day")