SlabSLAB, adjective Thick; viscous. [Not used.]SLAB, noun1. A plane or table of stone; as a marble slab2. An outside piece taken from timber in sawing it into boards, planks, _ c.3. A puddle. [See [[Slop]].]SLABS OF TIN, the lesser masses which the workers cast the metal into. These are run into molds of stone.