A monastery or convent established in England yet subject to a mother-house in another country, usually France. These were small establishments, sometimes with only two or three monks in residence. Their function was administrative, looking after the lands belonging to the mother-house. In 1294 many such properties were confiscated, at a time of war with France. In 1378 all the monks in alien priories were expelled, their lands being acquired by the crown.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.