Dictionary:

dubitable

  (dū'bĭ-tə-bəl, dyū'-)

Subject to doubt or question; uncertain.

[Latin dubitābilis, from dubitāre, to doubt. See doubt.]

adjective

Not affording certainty: ambiguous, borderline, chancy, clouded, doubtful, dubious, equivocal, inconclusive, indecisive, indeterminate, problematic, problematical, questionable, uncertain, unclear, unsure. Informal iffy. Idioms: at issue, in doubt, in question. See certain/uncertain, clear/unclear.

Definition: debatable
Antonyms: certain

The adjective has one meaning:

Meaning #1: open to doubt or suspicion
  Synonyms: doubtful, dubious, in question