If you plunk something somewhere, you put it there without great care.
例句
Melanie plunked her cosmetic case down on a chair...梅拉妮把化妆盒砰的一声扔到椅子上。She swept up a hat from where it had fallen on the ground, and plunked it on her hair.她拾起掉在地上的一顶帽子，随意地往头上一扣。
VERB
（使）砰地坐下；（使）重重地坐下
If you plunk yourself somewhere, or plunk down, you sit down heavily and clumsily.
例句
I watched them go and plunked down on one of the small metal chairs.我目送他们离去，然后一屁股坐在其中一把金属小椅子上。