1.
with a thud; plop; straight down (falling sound/manner)
Describes something falling or dropping suddenly and directly, often with a sound. An intensified form of すとんと. Conveys a clean, swift drop or fall.
I was so tired that as soon as I fell into bed, I dropped straight off to sleep.
An intensified or emphatic form of すとんと (with a thud, cleanly dropping). The っ adds a sense of suddenness or emphasis to the movement.