1. impervious or unpassable.   impermeable   ductile   discrete   indeterminate   Hint Half-n-half Clue   2. cancer-causing.   inverse   ductile   carcinogenic   buoyant   Half-n-half Clue   3. uncertain or not fixed   hypothetical   brittle   impenetrable   indeterminate   Half-n-half Clue   4. pertaining to the brain.   cerebral   inevitable   implicit   acrid   Half-n-half Clue   5. heat-liberating.   inductive   fundamental   calorific   anthropoid   Half-n-half Clue   6. practicable or possible.   concentric   feasible   determinate   inductive   Half-n-half Clue   7. limited or bounded.   finite   generic   determinate   aseptic   Half-n-half Clue