dem ‧ on ‧ stra ‧ tor AC /ˈdemənstreɪtə $ -ər/ BrE AmE noun [countable]
[ Word Family: noun : ↑ demonstration , ↑ demonstrator ; adverb : ↑ demonstrably , ↑ demonstratively ; adjective : ↑ demonstrable , ↑ demonstrative ; verb : ↑ demonstrate ]
1 . someone who takes part in a demonstration:
anti-war demonstrators
2 . someone who shows people how to do something or how something works