1. n. 
A mud with density high enough to produce a hydrostatic pressure at the point of influx in a wellbore that is sufficient to shut off flow into the well. Kill-weight mud, when needed, must be available quickly to avoid loss of control of the well or a blowout. Thus, it is usually made by weighting up some of the mud (link to ID 2107) in the system or in storage by adding barite or hematite. Unless diluted in advance, the mud may become too thick and perhaps un-pumpable due to high solids loading. A weight-up pilot test can identify if and how much dilution will be needed in advance of adding weighting material to the mud in the pits.
Alternate Form: kill-weight mud