Definition of "Code" :

noun: a coding system used for transmitting messages requiring brevity or secrecy

noun: (computer science) the symbolic arrangement of data or instructions in a computer program or the set of such instructions

noun: a set of rules or principles or laws (especially written ones)

verb: convert ordinary language into code

"We should encode the message for security reasons."

verb: attach a code to

"Code the pieces with numbers so that you can identify them later."