drain outlet; drain opening; overflow drain
Refers to the opening or outlet where water drains away, such as in a sink, bathtub, or floor. 'Overflow' refers to the secondary drain hole near the top of a bathtub or sink to prevent overflowing.
台所の排水口にゴミが詰まっている。
The kitchen drain is clogged with debris.
Don't forget to clean the bathtub drain.