What is another word for "improbable"?

Roget's Thesaurus (1911) lists these synonyms for "improbable": accessible, achievable, admit, against, agreement, all, and, any, anything, aquila, are, attainable, bad, bare, barely, bear, bizarre, but, chance, compatibility, compatible, conceivable, contingency, contingent, contrary, credible, dice, distance, doubtful, effect, expectation, far, feasibility, feasible, ghost, haply, have, heavy, improbability, inconceivable.