What is cop in british word?

"Cop" is not a common British word for a police officer. The most common terms are:

* Police officer (formal)

* Policeman/policewoman (more formal)

* Bobbie (informal, specifically for a London Metropolitan Police officer)

* Copper (informal, slang)

* The police (general term)

* Plod (derogatory slang)

So, while "cop" might be understood, it's not the typical term used in British English.