Meaning of “code” - Learner’s Dictionary

code

noun uk us /kəʊd/
SECRET MESSAGE [ C, U ]

B2 a set of letters, numbers, or signs that are used instead of ordinary words to keep a message secret:

The message was written in code.
They were trying to break (= understand) the enemy's code.
TELEPHONE [ C ] UK (UK/US area code)

a set of numbers used at the beginning of all the telephone numbers in a particular area

RULES [ C ]

a set of rules on how to behave or how to do things:

a code of conduct/practice
The club has a strict dress code (= rules about what you wear).
→ See also bar code , zip code

(Definition of “code” from the Cambridge Learner’s Dictionary © Cambridge University Press)