Plain English Meaning
A short code that stands for a pre-planned route between two airports. Instead of saying every fix and airway, you just give the code and everyone knows the full route it refers to.
Full Definition
A short alphanumeric code used by ATC and pilots to refer to a specific Tower En Route Control (TEC) route between two airports, in place of reading out the full routing. The code typically combines letters indicating the geographic area or city pair with a number identifying the specific route, and altitude category.
Context Anchor
Seen in Tower En Route Control route descriptions, usually when selecting or filing a short IFR route between nearby airports in busy terminal areas.
Derivation
"Coded" because the route has been reduced to a short label, and "identifier" because that label is what identifies which route is being used. The point is to replace a long routing description with one compact tag.