Then the body would be lifted up; there would be muttered directions, the wounded man would cry, then the other wounded would also cry-after that, there would be the dismal silence again, silence broken only by the shrapnel and the heavy Plopping smothers of the rain.
"The Dark Forest"
Hugh Walpole
Two dull, Plopping sounds came almost together.
"The Planet Strappers"
Raymond Zinke Gallun
He went out with a dull Plopping sound in his brain.
"Pursuit"
Lester del Rey