A scientist was someone who studied or practised sciences.
Scientist was one of the Sensorites' ranks on the Sense Sphere, and was denoted by a swirling pattern insignia worn on the chest of the scientists' grey bodysuits. Two Sensorite scientists treated John, the mineralogist on Captain Maitland's ship, to restore his mind after he was driven insane. (TV: The Sensorites)
Soldeed was the last surviving scientist and de facto leader of the planet Skonnos. He arranged a deal with the Nimon so Skonnos could conquer the galaxy. When he discovered the Nimon would not honour their agreement, he could not believe it. He was killed by Seth. (TV: The Horns of Nimon)
During the Thousand Year War on the planet Skaro, the Kaled race housed their Scientific Elite in a bunker, tasking them to produce inventions that would win them the war. Their leader, Davros engineered the Dalek race as the ultimate warrior. (TV: Genesis of the Daleks) The Daleks had their own scientistic castes such as the Temporal Research Team and the Dalek Scientific Division. (PROSE: Prisoner of the Daleks, AUDIO: The Genocide Machine, Return of the Daleks) Despite their importance, at least one scientist was regarded as a social outcast among the Daleks, abandoned in its laboratory. (AUDIO: Mutually Assured Destruction) In the New Dalek Paradigm, the Scientist Daleks were denoted by their orange casings. (TV: Victory of the Daleks)
When the Dalek Restoration Empire came to Mechanus to fight off the Entity, the Dalek Prime Strategist demanded to speak to a scientist, Mechanoid 2150 arriving to meet him. (WC: Planet of the Mechanoids)