Refers to an abbreviated symbol, code, or mark used to represent something concisely, such as in charts, maps, or technical contexts.
It's useful to learn the symbols on the map.
In this table, country names are indicated by codes.
telegraphic address; cable address
Compound of 略 (abbreviation) and 号 (mark, sign). The exact historical derivation is uncertain, but the kanji combination transparently conveys 'abbreviated mark'.