route beside a mountain stream
Refers to a path or trail that runs alongside a stream in mountainous terrain. Often used in hiking, geography, or nature descriptions.
As we climbed the path beside the mountain stream, a small waterfall came into view.
Compound of 沢 (sawa, 'mountain stream') and 筋 (suji, 'line, route'). The exact historical derivation is uncertain, but the meaning is transparent from its components.