adj. 25B6; adjective
the effects are uncertain : UNKNOWN, debatable, open to question, in doubt, undetermined, unsure, in the balance, up in the air; unpredictable, unforeseeable, incalculable; risky, chancy; informal iffy.
uncertain weather : CHANGEABLE, variable, changeful, irregular, unpredictable, unreliable, unsettled, erratic, fluctuating.
Ed was uncertain about the decision : UNSURE, doubtful, dubious, undecided, irresolute, hesitant, blowing hot and cold, vacillating, vague, unclear, ambivalent, in two minds.
an uncertain smile : HESITANT, tentative, faltering, unsure, unconfident.
predictable, sure, confident.