1. diurnal   based on experiment, not theory.   shaped like an oval; ambiguous or baffling.   of the day or daily.   impenetrable or unpassable.   Hint Half-n-half Clue   2. impervious   resembling man or man-like.   pertaining to the stars or spiritual.   pertaining to the back (of an animal).   impenetrable or unpassable.   Half-n-half Clue   3. combustible   periodic shedding (of leaves).   distinct or unconnected.   having cilia or minute hairs.   can catch fire or burn easily.   Half-n-half Clue   4. centrifugal   flying or radiating from a center.   resembling man or man-like.   tending to a center.   corresponding or in harmony.   Half-n-half Clue   5. centripetal   tending to a center.   concerned with nutrition.   of the universe; very large.   fragrant or sweet-smelling.   Half-n-half Clue   6. brittle   fragrant or sweet-smelling.   breakable or fragile.   cancer-causing.   not able to penetrate or understand.   Half-n-half Clue   7. heterodox   wearing away (by chemicals).   not conventional.   pertaining to the art of gardening.   surgically sterile or preventing infection.   Half-n-half Clue