indeterminably
  (ad.)不能決定地
  In·de·ter·mi·na·ble a.  Not determinable; impossible to be determined; not to be definitely known, ascertained, defined, or limited. -- In*de*ter*mi*na*bly, adv.
  indeterminably
       adv : in an indeterminable manner; "their relationship was of an
             indeterminably vague nature"