Denshi Jisho — Online Japanese dictionary

眠る ねむる 1: to sleep (not necessarily lying down);
2: to die;
3: (Archaism) to close one's eyes
Common word, Godan verb with ru ending, Intransitive verb 
眠る ねぶる 1: to sleep (not necessarily lying down);
2: (Archaism) to close one's eyes
Out-dated or obsolete kana, Godan verb with ru ending, Intransitive verb 

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