A mud that slows or stops hydration, swelling and disintegration of shales. A variety of mud types have been labeled as "inhibitive muds. " The degree of inhibition is not quantitative, but qualitatively they range from highly inhibitive (balanced-activity oil muds), moderately inhibitive (potassium muds and silicate muds), fairly inhibitive (calcium-based fluids) to slightly inhibitive (lignosulfonate, lignite water muds) to non-inhibitive (freshwater, nontreated muds).