letter card; aerogramme
A lightweight postal item that combines letter and envelope, often used for international airmail. Wasei-eigo from 'mini letter'.
wasei-eigo (Japanese-coined English), from mini letter
When sending a letter overseas, using a letter card is cheaper.
Wasei-eigo from English 'mini letter'. The exact origin is uncertain, but it likely emerged as a product name for a compact postal item.