to sit down suddenly and heavily, or to put an object or child down suddenly and without taking care

She plumped down next to me on the sofa. 她挨着我一屁股坐在沙发上。

He rushed in and plumped himself down in a chair. 他冲进房间，一屁股坐到椅子上。

Joan sat down at the front of the bus, and plumped her bags down beside her. 琼在公共汽车前部坐下，把行李放在身边。