The Collaborative International Dictionary of English v.0.48:

Lukewarm \Luke"warm`\ (l[=u]k"w[add]rm`), a. [See Luke.]
   1. Moderately warm; neither cold nor hot; tepid.
      [1913 Webster]

   2. Not ardent; not zealous; cool; indifferent. " Lukewarm
      blood." --Spenser. " Lukewarm patriots." --Addison.
      [1913 Webster]

            An obedience so lukewarm and languishing that it
            merits not the name of passion.       --Dryden.
      -- Luke"warm`ly, adv. -- Luke"warm`ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lukewarmness
    n 1: a warmness resembling the temperature of the skin [syn:
         lukewarmness, tepidity, tepidness]
    2: lack of passion, force or animation [syn: tepidness,
       lukewarmness]