Iffy propositions can be described by a variety of synonyms that convey their uncertain nature. One such synonym is dubious propositions, which means something that is doubtful or questionable. Another option is sketchy propositions, which implies that the information is incomplete or not entirely trustworthy. Risky propositions are those that carry potential hazards or unknown outcomes. Similarly, uncertain propositions carry the implication that the outcome is unclear or unpredictable. Shaky propositions suggest that the evidence or support for the proposition is weak or unstable. Finally, unconvincing propositions fail to persuade or convince their intended audience. All of these synonyms ultimately convey the idea that iffy propositions are not to be taken at face value and require careful consideration.