The Collaborative International Dictionary of English v.0.48:

Tepid \Tep"id\, a. [L. tepidus, fr. tepere to be warm; akin to
   Skr. tap to be warm, tapas heat.]
   Moderately warm; lukewarm; as, a tepid bath; tepid rays;
   tepid vapors. -- Tep"id*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tepid
    adj 1: moderately warm; "he hates lukewarm coffee"; "tepid bath
           water" [syn: lukewarm, tepid]
    2: feeling or showing little interest or enthusiasm; "a
       halfhearted effort"; "gave only lukewarm support to the
       candidate" [syn: halfhearted, half-hearted, tepid,
       lukewarm]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "tepid":
   Laodicean, aestival, apathetic, arid, blase, blood-hot, blood-warm,
   calid, cold, colorless, cool, dim, dull, equatorial, faint, feeble,
   fervorless, forceless, genial, halfhearted, indifferent, lifeless,
   luke, lukewarm, marrowless, mild, neuter, neutral, nonchalant,
   perfunctory, pithless, room-temperature, sapless, spiritless,
   subtropical, summery, sunny, sunshiny, temperate, thermal, thermic,
   toasty, tropical, uncaring, unconcerned, unenthusiastic, unfrozen,
   uninterested, unlively, warm, warm as toast, warmish, weak,
   zealless