Synonyms for Surefire:

• adj.

  •assured (adjective)
  • dependable,
  • fixed,
  • set,
  • decided,
  • undoubted,
  • sealed,
  • indubitable,
  • confirmed,
  • clear-cut,
  • clinched,
  • irrefutable,
  • secure,
  • ensured,
  • pronounced,
  • insured,
  • guaranteed,
  • unquestionable,
  • definite.
  •foolproof (adjective)
  • tried,
  • sure-fire,
  • goofproof,
  • idiot-proof,
  • tested,
  • safe,
  • unassailable.
  •guaranteed (adjective)
  • bonded,
  • ascertained,
  • endorsed,
  • attested,
  • for sure,
  • warranted,
  • secured,
  • protected,
  • certified,
  • have a lock on,
  • sure enough,
  • Plighted,
  • for a fact,
  • affirmed,
  • approved,
  • pledged.
  •incontrovertible (adjective)
  • established,
  • indisputable,
  • undeniable,
  • unshakable,
  • incontestable,
  • accurate,
  • authentic,
  • positive.
  •infallible (adjective)
  • omniscient,
  • faultless,
  • exact,
  • efficacious,
  • effective,
  • trustworthy,
  • flawless,
  • effectual,
  • authoritative,
  • true,
  • helpful,
  • satisfactory,
  • Undeceivable,
  • inerrable,
  • inerrant,
  • handy,
  • useful,
  • efficient,
  • unbeatable,
  • satisfying,
  • acceptable,
  • agreeable,
  • unimpeachable,
  • perfect,
  • apodictic,
  • impeccable,
  • correct.
  •predictable (adjective)
  • anticipated,
  • prepared,
  • foreseen,
  • foreseeable,
  • likely,
  • expected.
  •sure (adjective)
  • bound,
  • unerring,
  • irrevocable,
  • inescapable,
  • unavoidable,
  • ineluctable.
  •sure-fire (adjective)
  • excellent.
  •unfailing (adjective)
  • continuous,
  • constant,
  • never-failing,
  • tried-and-true,
  • consistent,
  • straight,
  • eternal,
  • diligent,
  • bottomless,
  • unlimited,
  • loyal,
  • assiduous,
  • same,
  • continuing,
  • there,
  • rock solid,
  • boundless,
  • ceaseless,
  • persistent,
  • continual,
  • dyed-in-the-wool,
  • unrelenting,
  • absolute,
  • Delivering,
  • invariable,
  • unflagging,
  • endless,
  • inexhaustible,
  • come-through,
  • counted on.

• n.

  •certainty (noun)
  • inevitability,
  • cinch,
  • all sewn up,
  • open and shut case,
  • dogmatism,
  • firmness,
  • conviction,
  • rain or shine,
  • surety,
  • steadiness,
  • definiteness,
  • certitude,
  • stock,
  • positivism,
  • staunchness,
  • belief,
  • shoo-in,
  • sureness,
  • setup,
  • Authoritativeness,
  • faith,
  • sure bet,
  • positiveness,
  • wrap-up,
  • lockup,
  • credence,
  • store,
  • inevitabilities,
  • validity,
  • confidence,
  • Indubitableness,
  • trust,
  • lock.
  •sure thing (noun)
  • foregone conclusion,
  • open-and-shut case,
  • small risk,
  • safe bet,
  • destiny,
  • sure-thing,
  • dead certainty,
  • CERTS,
  • cert.

• Other synonyms:

  •Other relevant words:
  • favorable,
  • predictable,
  • security,
  • inevitable,
  • responsible,
  • assurance,
  • fortunate,
  • reliable,
  • calculable,
  • coming,
  • fact,
  • successful,
  • sound,
  • triumphant,
  • explicit,
  • undisputable,
  • accountable,
  • actual,
  • foolproof,
  • fail-safe,
  • solid,
  • assured of success,
  • good,
  • prosperous,
  • well-grounded,
  • stable,
  • thorough,
  • watertight,
  • reliability,
  • faithful,
  • substantial,
  • succeeding,
  • staunch,
  • truth,
  • out in front,
  • can't-miss,
  • utter,
  • reality,
  • firm,
  • definitive,
  • trusty,
  • fast,
  • on top,
  • direct,
  • invincible,
  • steady,
  • made,
  • Faithworthy,
  • well-founded,
  • decisive,
  • steadfast,
  • certain,
  • confident,
  • affirmative.

Antonyms for Surefire:

• adj.

  • assured
    doubting, distrustful, hesitant, doubtful, indefinite, unfixed, undecided, uncertain, fearful, Feared, doubted, unsure, vague, confused, dismayed, nervous.
  • guaranteed
    disapproved, insecure.
  • incontrovertible
    questionable, changeable, Controvertible, variable.
  • infallible
    fallible, erring, imperfect, faulty.
  • predictable
    unexpected, improbable, unpredictable, unforeseen.
  • sure
    swerving, unsteady, wobbly, unself-confident, unconfident, dubious, humbled, wavering.
  • unfailing
    failing, changing, limited, impermanent.

• n.

  • certainty
    distrust, idea, doubt, disbelief, Questionableness, concept, uncertainty, theory, ambiguity, hesitation.