The Collaborative International Dictionary of English v.0.48:

Ticklish \Tic"klish\, a.
   1. Sensible to slight touches; easily tickled; as, the sole
      of the foot is very ticklish; the hardened palm of the
      hand is not ticklish. --Bacon.
      [1913 Webster]

   2. Standing so as to be liable to totter and fall at the
      slightest touch; unfixed; easily affected; unstable.
      [1913 Webster]

            Can any man with comfort lodge in a condition so
            dismally ticklish?                    --Barrow.
      [1913 Webster]

   3. Difficult; nice; critical; as, a ticklish business.
      [1913 Webster]

            Surely princes had need, in tender matters and
            ticklish times, to beware what they say. --Bacon.
      [1913 Webster] -- Tic"klish*ly, adv. --
      Tic"klish*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ticklish
    adj 1: difficult to handle; requiring great tact; "delicate
           negotiations with the big powers";"hesitates to be
           explicit on so ticklish a matter"; "a touchy subject"
           [syn: delicate, ticklish, touchy]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "ticklish":
   Herculean, abstruse, allergic, anaphylactic, arduous, awkward,
   brutal, capricious, changeable, complex, critical, dangerous,
   delicate, demanding, desultory, difficile, difficult, empathetic,
   empathic, exacting, fickle, formidable, fragile, goosy, hairy,
   hard, hard-earned, hard-fought, hazardous, high-strung,
   hyperesthetic, hyperpathic, hypersensitive, infirm, insecure,
   insubstantial, intricate, irritable, itchy, jawbreaking, knotted,
   knotty, laborious, mean, mercurial, miffy, nervous, no picnic,
   not easy, on slippery ground, on thin ice, operose, overrefined,
   oversensible, oversensitive, overtender, passible, perilous,
   precarious, prickly, provisional, refined, responsive, rigorous,
   risky, rocky, rough, rugged, sensitive, set with thorns, severe,
   shaky, shifting, shifty, skittish, slippery, slippy, spiny, steep,
   strenuous, supersensitive, sympathetic, tactful, temperamental,
   temporary, tender, tentative, tetchy, thin-skinned, thorny,
   tickling, tickly, titillative, toilsome, touch-and-go, touchy,
   tough, treacherous, tricky, uncertain, undependable, unfaithworthy,
   unreliable, unsettled, unsolid, unsound, unstable, unsteadfast,
   unsteady, unsubstantial, unsure, untrustworthy, uphill, variable,
   volatile, wicked