vacillating russian

• бесхребе́тный

  spineless, without backbone, weak, vacillating

• зы́бкий

  unsteady, vacillating

• коле́блющийся

  vacillating, wavering, indecisive

  swaying, wavering, flickering, fluctuating

• колебательно

  oscillatingly, hesitantly, vacillatingly