The crossword solution for the term RCHIN is IMP, which stands for Imperial Measurement. Imperial Measurement is a system of units used in the United Kingdom and other Commonwealth countries. It is based on the imperial system of units, which was established in 1824 and is still used today. The system includes units such as feet, inches, pounds, and gallons. Imperial Measurement is still widely used in the UK and other Commonwealth countries, although it has been largely replaced by the metric system in most other countries.