Synonyms for Debatable (same or very similar meaning)
WordNet sense 1 (open to doubt or debate):
problematic, problematicalWordNet sense 2 (subject to question):
questionableWordNet sense 3 (open to argument or debate):
arguable, disputable, mootWordNet sense 4 (marked by or capable of arousing controversy):
controversialFrom the ODE community, based on WordNetadd/edit