special constablenoun [ C ]
also Special Constable uk/ˌspeʃ.əl ˈkʌn.stə.bəl//ˌspeʃ.əl ˈkɑːn.stə.bəl/also informal special, Specialin the UK, a person who is not a paid member of the police force but who wears a police uniform and is trained to act as a police officer in certain situations:
Why not volunteer as a special constable and support the work of your police force in the community?
There are nearly 20,000 Specials serving with police forces across the UK.