1. An expert who gives advice; SYN. advisor, consultant.
2. A counselor; SYN. advisor, consultant.

An expert who gives advice

An expert who is called in to advise a business or other organization about various aspects of its operations.
A computer professional who deals with client firms as an independent contractor rather than as an employee. Consultants are often engaged to analyze user needs and develop system specifications.

One who consults, one who asks for advice