1. n. []

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

See related terms: blowout preventer,  casing string