Look up selion in Wiktionary, the free dictionary.
Selion is a medieval open strip of land or small field used for growing crops, usually owned by or rented to peasants. A selion of land was typically one furlong (660 ft) long and one chain (66 ft) wide. However, exact measurements could vary depending on geography of the land. The area of one furlong by one chain is one acre. Monasteries or similar institutions were often bequeathed selions and then derived an income from them by letting.