This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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verb-intransitive. To sleep.

verb-intransitive. To be dormant or quiescent.

v. To pass (time) in sleep: slumbered the night away.

n. Sleep.

n. A state of inactivity or dormancy.

n. A very light state of sleep, almost awake.

v. To be in a very light state of sleep, almost awake

v. To be inactive

verb-intransitive. To sleep; especially, to sleep lightly; to doze.

verb-intransitive. To be in a state of negligence, sloth, supineness, or inactivity.

v. To lay to sleep.

v. To stun; to stupefy.

n. Sleep; especially, light sleep; sleep that is not deep or sound; repose.

To grow sleepy or drowsy; begin to sleep; fall asleep; also, to sleep lightly; doze.

To sleep; sleep quietly.

To be in a state of negligence, sloth, supineness, or inactivity.

Synonyms and 2. Drowse, Doze, etc. See sleep.

To lay to sleep; cause to slumber or sleep.

To stun; stupefy.

To cause to be latent; keep as if in a sleeping condition.

n. Light sleep; sleep not deep or sound.

n. Sleep, especially sound sleep.

n. A sleeping state; sleep regarded as an act.

n. a dormant or quiescent state

n. a natural and periodic state of rest during which consciousness of the world is suspended

v. be asleep

"Waking up at 2: 30 without the power to fall back into slumber is disconcerting."

sloom   

slumbered    slumbering    slumbers   

quiescence    dormancy    quiescency   

slumber party    catnap    nap    doze    shuteye   

slumbered    slumbering   

sleep    doze    stun    stupefy    repose    slee   

Humber    cumber    encumber    lumber    number    outnumber    unencumber   

sleep    stupor    repose    trance    reverie    unconsciousness    stillness    lethargy    doze    oblivion