Causing one to believe what is not true or fail to believe what is true:
— Deceptive calm.

synonym: delusory.

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

Roget 545: deceived etc. v.; deceiving &c.; cunning etc. 702; prestigious^†, prestigiatory^†; deceptive, deceptious^†; deceitful, covinous^†; delusive, delusory; illusive, illusory; elusive, insidious, ad captandum vulgus [Lat.].    untrue etc. 546; mock, sham, make-believe, counterfeit, snide [Slang], pseudo, spurious, supposititious, so-called, pretended, feigned, trumped up, bogus, scamped, fraudulent, tricky, factitious bastard; surreptitious, illegitimate, contraband, adulterated, sophisticated; unsound, rotten at the core; colorable; disguised; meretricious, tinsel, pinchbeck, plated; catchpenny; Brummagem.    artificial, synthetic, ersatz [G.]; simulated etc. 544.    ... show more

Designed to deceive or mislead either deliberately or inadvertently:
— The deceptive calm in the eye of the storm.
— Deliberately deceptive packaging.

synonym: misleading.