1) Foul or dirty; a very common specific in minor place-names, especially in combinations descriptive of lanes and water courses.
Typical names listed by Smith are Foulcauseway Slack in Fewston and Foul Sike in Dent. Early references include: c.1210 terre Lazarorum de fulsnap, Pontefract
1321 a selion called Foulsikeland, Adlingfleet. Such names could develop at any time: 1686 a great hole called the fowle hole worne by the overflowing of the river in the highway, 60 yards longe, 2 yards over and one quarter yard deep, Kirkstall.