consultant

noun4

1. •
   A person or party that is consulted.
2. •
   A person whose occupation is to be consulted for their expertise, advice, service or help in an area or specialty; a party whose business is to be similarly consulted.
3. •
   (US, Canada) Synonym of informant.
4. •
   (UK, Ireland) A senior hospital-based physician or surgeon who has completed all specialist training and has been placed on the specialist register in their chosen speciality, roughly equivalent to an attending physician in North America.