1. n. [Drilling Fluids]
A cellulose derivative similar in structure, properties and usage in drilling fluids to carboxymethylcellulose. PAC is considered to be a premium product because it typically has a higher degree of carboxymethyl substitution and contains less residual NaCl than technical grade carboxymethylcellulose, although some PACs contain considerable NaCl.
Alternate Form: PAC
See: calcium carbonate, carboxymethylcellulose, potassium mud