Likely to fail or make errors.

Roget 475: uncertain; casual; random etc. (aimless) 621; changeable etc. 149.    doubtful, dubious; indecisive; unsettled, undecided, undetermined; in suspense, open to discussion; controvertible; in question etc. (inquiry) 461.    vague; indeterminate, indefinite; ambiguous, equivocal; undefined, undefinable; confused etc. (indistinct) 447; mystic, oracular; dazed.    perplexing etc. v.; enigmatic, paradoxical, apocryphal, problematical, hypothetical; experimental etc. 463.    unpredictable, unforeseeable (unknowable) 519.    fallible, questionable, precarious, slippery, ticklish, debatable, disputable; unreliable, untrustworthy.    contingent, contingent on, dependent on; subject to; dependent on circumstances; occasional; provisional.    unauthentic, unauthenticated, unauthoritative; unascertained, unconfirmed; undemonstrated; untold, uncounted.    in a state of uncertainty, in a cloud, in a maze; bushed, off the track; ignorant, etc. 491; afraid to say; out of one's reckoning, astray, adrift; at sea, at fault, at a loss, at one's wit's end, at a nonplus; puzzled etc. v.; lost, abroad, d_esorient_e; distracted, distraught.    ... show more

Roget 485: unbelieving; skeptical, sceptical.    incredulous as to, skeptical as to; distrustful as to, shy as to, suspicious of; doubting etc. v.. doubtful etc. (uncertain) 475; disputable; unworthy of, undeserving of belief etc. 484; questionable; suspect, suspicious; open to suspicion, open to doubt; staggering, hard to believe, incredible, unbelievable, not to be believed, inconceivable; impossible etc. 471.    fallible etc. (uncertain) 475; undemonstrable; controvertible etc. (untrue) 495.    ... show more

Wanting in moral strength, courage, or will; having the attributes of man as opposed to e.g. divine beings:
— I'm only a fallible human.

synonyms: frail, imperfect, weak.

Roget 477: intuitive, instinctive, impulsive; independent of reason, anterior to reason; gratuitous, hazarded; unconnected.    unreasonable, illogical, false, unsound, invalid; unwarranted, not following; inconsequent, inconsequential; inconsistent; absonous^†, absonant^†; unscientific; untenable, inconclusive, incorrect; fallacious, fallible; groundless, unproved; non sequitur [Lat.], it does not follow.    deceptive, sophistical, jesuitical; illusive, illusory; specious, hollow, plausible, ad captandum [Lat.], evasive; irrelevant etc. 10.    weak, feeble, poor, flimsy, loose, vague.    irrational; nonsensical etc. (absurd) 497.    foolish etc. (imbecile) 499; frivolous, pettifogging, quibbling; finespun^†, overrefined^†.    at the end of one's tether, au bout de son latin.    ... show more