noun, noun or participle which takes 'suru'
sleeping away from home; overnight stay while traveling
Refers to lodging overnight during a journey, often with a slightly literary or poetic feel. Can be used as a noun or with する to mean 'to stay overnight on a trip'.
旅寝の夜は、なかなか寝つけなかった。
On nights sleeping away from home, I couldn't fall asleep easily.
昔の旅人は、野宿で旅寝
Travelers in the old days often slept outdoors during their journeys.