unreliable

unreliable
    adj 1: liable to be erroneous or misleading; "an undependable
           generalization" [syn: {undependable}, {unreliable}]
    2: not worthy of reliance or trust; "in the early 1950s
       computers were large and expensive and unreliable"; "an
       undependable assistant" [syn: {unreliable}, {undependable}]
       [ant: {dependable}, {reliable}]
    3: dangerously unstable and unpredictable; "treacherous winding
       roads"; "an unreliable trestle" [syn: {treacherous},
       {unreliable}]
    4: lacking a sense of responsibility
    

Unreliable \Un`re*li"a*ble\, a.
   Not reliable; untrustworthy. See {Reliable}. --
   {Un`re*li"a*ble*ness}, n.
   [1913 Webster]

         Alcibiades . . . was too unsteady, and (according to
         Mr. Coleridge's coinage) "unreliable;" or perhaps, in
         more correct English, too "unrelyuponable." --De
                                                  Quincey.
   [1913 Webster]
    

134 Moby Thesaurus words for "unreliable":
      adrift, afloat, alternating, amorphous, capricious, changeable,
      changeful, coquettish, dangerous, desultory, deviable,
      disreputable, dizzy, doubtful, dubious, eccentric, erratic,
      faddish, faithless, false, falsehearted, fast and loose, fickle,
      fitful, flickering, flighty, flimsy, flirtatious, flitting,
      fluctuating, fly-by-night, freakish, garbled, giddy, hazardous,
      impetuous, impulsive, inaccurate, inauthentic, inconsistent,
      inconstant, indecisive, inexact, infirm, insecure, insubstantial,
      irregular, irresolute, irresponsible, light, mazy, mercurial,
      miscited, misquoted, misreported, misstated, moody, perfidious,
      perilous, precarious, provisional, questionable, quicksilver,
      rambling, restless, risky, rocky, roving, scatterbrained, shaky,
      shapeless, shifting, shifty, shuffling, skittish, slick, slippery,
      spasmodic, spineless, spurious, temporary, tentative, ticklish,
      tottery, toying, treacherous, tricky, trustless, unaccountable,
      unassured, unauthentic, unauthoritative, uncertain, uncontrolled,
      undependable, undisciplined, unfaithful, unfaithworthy, unfixed,
      unfounded, unhealthy, unpredictable, unrestrained, unsafe,
      unsettled, unsolid, unsound, unstable, unstable as water, unstaid,
      unsteadfast, unsteady, unsubstantial, unsure, untrue,
      untrustworthy, untrusty, vacillating, vagrant, variable, versatile,
      vicissitudinary, vicissitudinous, volatile, wandering, wanton,
      wavering, wavery, wavy, wayward, weak, whimsical, wishy-washy,
      workaday