open to question (?.)

• arguable
• at issue
• confutable
• conjectural
• contestable
• controversial
• controvertible
• debatable
• deniable
• disputable
• doubtable
• doubtful
• dubious
• dubitable
• iffy
• in dispute
• in doubt
• in dubio
• in question
• mistakable
• moot
• open to doubt
• problematic
• questionable
• refutable
• speculative
• suppositional
• suspect
• suspicious