A thermologist was a type of scientist.
In 2369, thermologists were involved in the conversion of the Bajoran moon Jeraddo into a power plant. Jadzia Dax initially attributed an aberrant humanoid life sign to one of these scientists, although in reality it was Mullibok. Later, Kira Nerys told Dax she was staying to have supper with the man, saying she'd have one of the thermologists bring her back instead of riding with the Trill on the USS Ganges. (DS9: "Progress")