drainstopper
nounUK /ˈdreɪnˌstɒpə/
US /ˈdreɪnˌstɑːpər/
A drainstopper is a small plug that keeps water in a sink or tub.
She pulled out the drainstopper so the dirty water could go down.
OTHER MEANINGS
2. A device or person that blocks or slows something down.
The broken machine became a drainstopper for the whole assembly line.
3. A removable cap fitted into a drain opening to seal it.
He replaced the old rubber drainstopper with a new metal one.
4. Something that prevents progress or flow, used figuratively.
Red tape acted as a drainstopper on the project.