1. n. 
A chemical injected into the wellbore to prevent or minimize paraffin deposition. The effectiveness of paraffin inhibitors is strongly dependent on crude oil composition. Paraffin inhibitors must be introduced into the oil before the oil cools to its cloud point. In additional, asphaltene composition should be determined before treatment because it can reduce the effectiveness of the paraffin inhibitor. In some cases, the use of a paraffin inhibitor can actually increase the rate of paraffin deposition because the stability of colloidal asphaltenes is disturbed.
See: organic deposit