a.
1.
Equivocal, doubtful, dubious, unsettled, indistinct, ambiguous, indefinite, questionable.
2.
Unreliable, insecure, precarious, problematical.
3.
Not sure, not confident, doubtful, dubious.
4.
Irregular, unpunctual, capricious, desultory, fitful, variable, changeable, mutable, slippery, shaky, unsettled.