Definitions

1. noun

A pipe or passageway in a nuclear reactor or a distillation column that carries a liquid downward.

“The downcomer in the nuclear reactor was inspected regularly for signs of corrosion.”

2. noun

A pipe or channel that carries a liquid downward in a distillation process, such as a distillation column in an oil refinery.

“The downcomer in the oil refinery was cleaned to prevent contamination of the product.”