noun, noun or participle which takes 'suru', intransitive verb
comfortable sleep; restful sleep
Refers to sleeping comfortably and restfully, often implying a relaxed, carefree sleep.
休日は朝まで楽寝したい。
On holidays I want to sleep in comfortably until morning.
新しい布団で楽寝できた。
I was able to get a comfortable sleep with the new futon.
安眠 is a more common word for peaceful sleep, while 楽寝 emphasizes the comfort and ease of sleeping.
Compound of 楽 (らく, 'comfort') and 寝 (ね, 'sleep'). The exact historical derivation is uncertain, but the word is transparently formed from these elements.