plonked

Plonked is the past tense of plonk, a verb meaning to set something down heavily or carelessly.

She plonked the groceries on the counter and collapsed into a chair.

The word suggests a lack of ceremony or precision—you don't plonk fine china, you plonk a six-pack.

In British usage, if you plonk yourself somewhere, you sit or drop down without much grace.

The word is echoic, mimicking the dull thud of something landing.