consultant(n = noun.person) adviser, advisor - an expert who gives advice; "an adviser helped students select their courses"; "the United States sent military advisors to Guatemala"
is a kind of authority
has particulars: amicus curiae, friend of the court, backroom boy, brain truster, beauty consultant, counsellor, counselor, agricultural agent, county agent, extension agent, fashion consultant, fashionmonger, investment adviser, investment advisor, management consultant, media consultant, media guru, military adviser, military advisor, security consultant, starets, tipster, tout
Derived forms verb consult₄, noun consultancy₁

   an expert who gives advice. [WordNet 1.5]

consultant, n.
1 a person providing professional advice etc., esp. for a fee.
2 a senior specialist in a branch of medicine responsible for patients in a hospital.

Etymology:
prob. F (as consult)

beauty consultant, fashion consultant, management consultant, media consultant, security consultant