The Collaborative International Dictionary of English v.0.48:

Benumb \Be*numb"\, v. t. [imp. & p. p. Benumbed; p. pr. & vb.
   n. Benumbing.] [OE. binomen, p. p. of binimen to take away,
   AS. beniman; pref. be + niman to take. See Numb, a., and
   cf. Benim.]
   To make torpid; to deprive of sensation or sensibility; to
   stupefy; as, a hand or foot benumbed by cold.
   [1913 Webster]

         The creeping death benumbed her senses first. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

benumb
    v 1: make numb or insensitive; "The shock numbed her senses"
         [syn: numb, benumb, blunt, dull]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "benumb":
   KO, abate, allay, alleviate, anesthetize, appease, assuage, bedaze,
   bemuse, besot, bite, blunt, chill, chloroform, coldcock, cushion,
   cut, deaden, deaden the pain, desensitize, diminish, dope, drug,
   dull, ease, ease matters, etherize, foment, freeze, frost,
   frostbite, give relief, go through, kayo, knock out,
   knock senseless, knock stiff, knock unconscious, lay, lay out,
   lessen, lull, mitigate, mollify, mull, narcotize, nip, numb,
   obtund, pad, palliate, palsy, paralyze, penetrate, petrify, pierce,
   poultice, pour balm into, pour oil on, put to sleep, reduce,
   refrigerate, relieve, salve, slacken, slake, soften, soothe, stun,
   stupe, stupefy, subdue