noun
Refers to a light, brief sleep, often during the day or when one is not fully asleep. More literary or poetic than 居眠り.
午後の陽だまりで、猫がまどろみに落ちていた。
In the afternoon sun, the cat had fallen into a doze.
電車の中で短いまどろみを楽しんだ。
I enjoyed a short nap on the train.
居眠り is a more common, everyday word for dozing off, especially unintentionally (e.g., in class or at work). まどろみ is more literary and often implies a pleasant, light sleep.
うたた寝 also means a nap or doze, but often refers to dozing off unintentionally while sitting or lying down. まどろみ emphasizes the state of light sleep itself.
The word まどろみ is derived from the verb まどろむ (to doze). The kanji 微睡 are jukujikun, assigned for their meanings ('faint' and 'sleep') rather than their usual readings.