1. n. 
A thinning agent used to reduce viscosity or prevent flocculation; incorrectly called a "dispersant." Most deflocculants are low-molecular-weight anionic polymers that neutralize positive charges on clay edges. Examples include polyphosphates, lignosulfonates, quebracho, and various water-soluble synthetic polymers.
See: acrylamide polymer, acrylate polymer, Bingham plastic model, bland coring fluid, carbonate ion, chrome lignosulfonate, chrome-free, clay-water interaction, conventional mud, deflocculated mud, direct-indicating viscometer, drill solids, gel strength, gyp mud, kill-weight fluid, lignin, lignite, lignosulfonate, phosphate salt, plastic viscosity, polar compound, polymer, red mud, rheology, SAPP, sulfonated polystyrene-maleic anhydride copolymer, tannic acid, tannin, yield point