The Collaborative International Dictionary of English v.0.48:

Slabby \Slab"by\, a. [Compar. Slabbier; superl. Slabbiest.]
   [See Slab, a.]
   1. Thick; viscous.
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            They present you with a cup, and you must drink of a
            slabby stuff.                         --Selden.
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   2. Sloppy; slimy; miry. See Sloppy. --Gay.
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