Answer:

kerplunk

Answer	Crossword Clue
KERPLUNK	With a thud
KERPLUNK	Plopping sound
KERPLUNK	With a thud.

KERPLUNK	Dropping sound
KERPLUNK	... a raindrop in a puddle
KERPLUNK	Plop's kin

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.