The Collaborative International Dictionary of English v.0.48:

Insulate \In"su*late\, v. t. [imp. & p. p. Insulated; p. pr. &
   vb. n. Insulating.] [L. insulatus insulated, fr. insula
   island. See Isle, and cf. Isolate.]
   [1913 Webster]
   1. To make an island of. [Obs.] --Pennant.
      [1913 Webster]

   2. To place in a detached situation, or in a state having no
      communication with surrounding objects; to isolate; to
      separate.
      [1913 Webster]

   3. (Elec. & Thermotics) To prevent the transfer of
      electricity or heat to or from (bodies) by the
      interposition of nonconductors.
      [1913 Webster]

   Insulating stool (Elec.), a stool with legs of glass or
      some other nonconductor of electricity, used for
      insulating a person or any object placed upon it.
      [1913 Webster]

WordNet (r) 3.0 (2006):

insulate
    v 1: protect from heat, cold, or noise by surrounding with
         insulating material; "We had his bedroom insulated before
         winter came"
    2: place or set apart; "They isolated the political prisoners
       from the other inmates" [syn: isolate, insulate]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "insulate":
   bolt, close off, cordon, cordon off, cover, cull out, cushion,
   cut off, detach, divide, enisle, fireproof, ghettoize, gin, ground,
   island, island-hop, isolate, keep apart, keep aside, lag,
   lay aside, pick out, preserve, proof, protect, put aside,
   quarantine, riddle, screen, seclude, segregate, separate,
   sequester, sequestrate, set apart, set aside, shelter, shield,
   sieve, sift, sort out, soundproof, thrash, thresh, waterproof,
   weatherproof, winnow, wrap