decisive; critical

critical, important

that can be argued about because uncertain

controversial

(of a person) feeling doubt

doubtful

not safe; not providing good support; not to be relied on

uncertain, worried

uncertain; unsafe; depending on chance

tricky, doubtful

not reliable; not certainly knowing or known

doubtful, changeable

not predictable

changeable

not safe

dangerous

not confident; not certain or reliable

doubtful, insecure

important and so needing a quick decision or action; (of a person, voice etc) showing that something is urgent

needing immediate attention