Iffier is the comparative form of iffy, meaning more uncertain, doubtful, or questionable: The weather looks even iffier than yesterday.
Something iffier involves greater risk or less reliability: The second plan seemed iffier than the first.
1. comparison — shakier, More unsteady or unstable; riskier (More prone to danger); dicier (More uncertain or hazardous); dodgier (More evasive or unreliable); sketchier · chancier · wobblier
2. instability — shakier, More unsteady or unstable; wobblier (More prone to teetering)
3. risk — riskier, More prone to danger; chancier (More subject to uncertainty); dicier (More uncertain or hazardous)