Constable

1. One holding the lowest rank in most Commonwealth police forces. (See also chief constable.)
2. A police officer or an officer with equivalent powers.
3. An officer of a noble court in the Middle Ages, usually a senior army commander. (See also marshal).
4. The warden of a castle.
5. A public officer, usually at municipal level, responsible for maintaining order or serving writs and court orders.
6. (Channel Islands) An elected head of a parish (also known as a connétable)
7. A large butterfly, Dichorragia nesimachus, family Nymphalidae, of Asia.

verb

To act as a constable or policeman.