(treated as sing. or pl) a body of trained people entrusted by a government with maintenance of public order and enforcement of laws

(treated as pl) members of this body; police officers

call the police

(treated as sing. or pl) an organized body having similar functions within a more restricted sphere

railway police

informal a group considering itself to be arbiters of right and wrong in fashion, morality, language, etc

to control (an area, event, etc) by use of police

to supervise the operation or administration of (e.g. an industry or election), esp to prevent violation of rules