The sound made by knocking on a door with a hard object (such as a door knocker).(interjection)
The sound made by firing an automatic machine gun.(interjection)
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Use "rat-tat-tat" in a sentence
"From above came the slapping of canvas and the quivering rat-tat-tat of the after leech of the loosely stretched foresail."
"It is through interviewing World War II veterans that he find the telling details that give narrative history a heartbeat and enable it to rise above the rat-tat-tat chronology of an after-action report."
"From on deck came the jar of sheet-blocks and the rat-tat-tat of the reef-points against the canvas."