The term 'Jack in Oaters' is a phrase used to describe a type of western film popularized in the 1930s and 1940s. The crossword solution for this term is ELAM, which stands for Edward Lamson Henry, an American painter who specialized in depicting scenes from the American West. He was known for his paintings of cowboys, Native Americans, and other figures from the Old West, which were often used as the basis for Jack in Oaters films.