A person who takes part in a public protest or march to express an opinion or support a cause. The demonstrator held a sign demanding climate action during the rally.
A person who shows how a product or skill works, often as part of a sales or educational presentation. The demonstrator at the trade show explained the features of the new kitchen appliance.
An apparatus or device employed to demonstrate a principle, process, or product. The engineering lab keeps a fluid-flow demonstrator to show students how turbines work.
In some universities, a postgraduate assistant who supervises laboratory classes and demonstrates experimental procedures. The chemistry demonstrator guided first-year students through the titration experiment.