specialist

adj

1. (British)Specialised, involving detailed knowledge of a restricted topic.

   “This was a highly specialist job, and it has been very carefully carried out so that it is very hard to see that these windows are now modern replacements.”

noun

1. Someone who is an expert in, or devoted to, some specific branch of study or research.
2. A player on a team who primarily employs one particular skill or takes one particular role.
3. A physician whose practice is limited to a particular branch of medicine or surgery.

   “Dr. Robert Leroy Hutton, a retired specialist in internal medicine and a well‐known diagnostician, died yesterday here.”

   “Most Americans mistakenly believe that they must see specialists for almost every medical problem.”

4. (US)Any of several non-commissioned ranks corresponding to that of corporal.
5. An organism that is specialized for a particular environment.

   “The tree Lepidothamnus laxifolius is a high alpine specialist found in high-altitude bog communities and in scrub.”

6. A stenotopic species.
7. A sixth-former at Eton College.