The Collaborative International Dictionary of English v.0.48:

Slumber \Slum"ber\, v. i. [imp. & p. p. Slumbered; p. pr. &
   vb. n. Slumbering.] [OE. slombren, slumberen, slumeren, AS.
   slumerian, fr. sluma slumber; akin to D. sluimeren to
   slumber, MHG. slummern, slumen, G. schlummern, Dan. slumre,
   Sw. slumra, Goth. slawan to be silent.]
   1. To sleep; especially, to sleep lightly; to doze. --Piers
      Plowman.
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            He that keepeth Israel shall neither slumber nor
            sleep.                                --Ps. cxxi. 4.
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   2. To be in a state of negligence, sloth, supineness, or
      inactivity. "Why slumbers Pope?" --Young.
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The Collaborative International Dictionary of English v.0.48:

Slumber \Slum"ber\, v. t.
   1. To lay to sleep. [R.] --Wotton.
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   2. To stun; to stupefy. [Obs.] --Spenser.
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The Collaborative International Dictionary of English v.0.48:

Slumber \Slum"ber\, n.
   Sleep; especially, light sleep; sleep that is not deep or
   sound; repose.
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         He at last fell into a slumber, and thence into a fast
         sleep, which detained him in that place until it was
         almost night.                            --Bunyan.
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         Fast asleep? It is no matter;
         Enjoy the honey-heavy dew of slumber.    --Shak.
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         Rest to my soul, and slumber to my eyes. --Dryden.
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WordNet (r) 3.0 (2006):

slumber
    n 1: a natural and periodic state of rest during which
         consciousness of the world is suspended; "he didn't get
         enough sleep last night"; "calm as a child in dreamless
         slumber" [syn: sleep, slumber]
    2: a dormant or quiescent state
    v 1: be asleep [syn: sleep, kip, slumber, log Z's,
         catch some Z's] [ant: wake]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "slumber":
   ataraxia, ataraxy, beauty sleep, beddy-bye, bedtime, blanket drill,
   bye-bye, calmness, coma, composure, contemplation, dorm, doss,
   doze, dreamland, drowse, dullness, fitful sleep, fust, hang fire,
   hebetude, hibernation, idle, imperturbability, land of Nod,
   languor, lassitude, light sleep, lucid stillness, marmoreal repose,
   nap, nirvana, oversleep, peace, peacefulness, placidity,
   placidness, quiescence, quiescency, quiet, quietism, quietness,
   quietude, repose, rest, restfulness, satori, saw logs, saw wood,
   serenity, shut-eye, silence, silken repose, sleep, sleep soundly,
   sleepland, sleepwalking, slumberland, smolder, snoozle, snore,
   somnambulism, somniloquy, somnus, stagnate, stillness, stupor,
   take a nap, torpidity, torpor, tranquillity, unconsciousness,
   vegetate, winter sleep, wise passiveness