(n.) An assertion that seems contradictory, but may in fact be true; as, the paradox that standing is harder work than walking\; that which in appearance or terms is absurd, but yet may be true in fact.

Gordian knot absurdity ambiguity ambivalence antinomy asymmetry contradiction crux dilemma disproportion disproportionateness enigma equivocality equivocation heresy heterodoxy heterogeneity hopelessness impossibility impossible impossibleness incoherence incommensurability incompatibility inconceivability incongruity inconsistency inconsonance irony irreconcilability knot knotty point mystery no chance node nodus nonconformability nonconformity nonplus oxymoron perplexity pons asinorum poser problem puzzle quandary self-contradiction teaser the impossible unconformability unconformity unimaginability unorthodoxy unthinkability vexed question what cannot be what cannot happen