wandering monk; itinerant monk on pilgrimage
A yojijukugo describing a Zen monk traveling on foot to many places for training and pilgrimage. Often used in Buddhist contexts.
In his youth, he set out on a journey as a wandering monk.
行脚 alone means pilgrimage or traveling on foot, often for religious training. 雲水行脚 specifically refers to a Zen monk's wandering pilgrimage.
雲水 literally means 'clouds and water' and is a term for a traveling Zen monk. 雲水行脚 combines this with 行脚 (pilgrimage).
Compound of 雲水 (unsui, 'clouds and water', a term for a traveling Zen monk) and 行脚 (angya, 'pilgrimage, traveling on foot'). The exact historical derivation is uncertain; the phrase is a yojijukugo used in Zen Buddhism.