1. n. [Well Completions]
The process of disassembling well-control or pressure-control equipment on the wellhead. Depending on the configuration of the wellhead and casing strings, it may be necessary to nipple-down and nipple-up the blowout preventer (BOP) system as each casing string is run.
Antonyms: nipple up, nipple-up
Alternate Form: nipple down
