Frown: In razor talk, this is when the ends of the edge curve down, when the blade is held horizontal with the edge down. Or can simply be any area of the edge, away from the ends, that causes an upward arch. Neither are considered a good thing in a razor edge, and should be corrected any time a razor is honed. A little smile at the ends is considered OK.
Slurry: When you rub two honing stones together with water(usually finer stones) you will get a slurry, a cloundy substance in place of the water, which caries particles from the stones. This slurry will help the stone to cut faster, but not quite as fine. Many hone masters use this to get the work done, then follow with clear water to get to the super fine finish.