Being an intellectual is an occupational category — those people whose work starts and ends with ideas and no other output. These ideas may be highly influential and may eventually cause tangible things to happen in the hand of others.
Think of philosophers, certain professors, authors, speakers, and certain journalists.
Brain surgeons and engineers are not intellectuals. Their work is challenging, and it requires a capacity to understand complex ideas and the ability to have studied for years on end. They are not intellectual because their final output is tangible, a manipulation of someone’s brain to help save their life or the construction of a bridge.
Being an intellectual does not mean that you are intelligent or superior. You can have bad policemen, but they are still policemen.