The Collaborative International Dictionary of English v.0.48:

Irresolute \Ir*res"o*lute\, a. [Pref. ir- not + resolute: cf. F.
   irr['e]solu, L. irresolutus not loosened.]
   Not resolute; not decided or determined; wavering; given to
   doubt or irresolution.
   [1913 Webster]

         Weak and irresolute is man.              --Cowper.

   Syn: Wavering; vacillating; undetermined; undecided;
        unsettled; fickle; changeable; inconstant. --
        Ir*res"o*lute*ly, adv. -- Ir*res"o*lute*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

irresolute
    adj 1: uncertain how to act or proceed; "the committee was timid
           and mediocre and irresolute" [ant: resolute]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "irresolute":
   adrift, afloat, agnostic, alternating, ambiguous, ambitendent,
   ambivalent, amorphous, at loose ends, bland, capricious, chancy,
   changeable, changeful, changing, desultory, deviable, dicey, dizzy,
   double-minded, doubting, dubious, eccentric, equivocal, erratic,
   faltering, fast and loose, fence-sitting, fence-straddling, fickle,
   fitful, flickering, flighty, flitting, fluctuating, freakish,
   giddy, halfhearted, halting, hesitant, hesitating, impetuous,
   impulsive, incalculable, inconsistent, inconstant, indecisive,
   indemonstrable, infirm, infirm of purpose, infirm of will, insipid,
   irregular, irresolved, irresponsible, mazy, mercurial,
   milk-and-water, milky, moody, mugwumpian, mugwumpish, mushy,
   mutable, neutral, of two minds, polysemous, rambling, restless,
   roving, scatterbrained, shapeless, shifting, shifty,
   shilly-shallying, shuffling, skeptical, spasmodic, spineless,
   tasteless, tentative, touch-and-go, unaccountable, uncertain,
   unconfirmable, uncontrolled, unconvinced, undecided, undependable,
   undetermined, undisciplined, undivinable, unfixed, unforeseeable,
   unpersuaded, unpredictable, unprovable, unreliable, unresolved,
   unrestrained, unsettled, unstable, unstable as water, unstaid,
   unsteadfast, unsteady, unsure, unverifiable, vacillating,
   vacillatory, vagrant, vapid, variable, vicissitudinary,
   vicissitudinous, volatile, wandering, wanton, watery, wavering,
   wavery, wavy, wayward, whimsical, wishy-washy, wobbly