Definition: to operate a motor vehicle at high speed or so as to create a great deal of engine noise
We now so associate the word vroom with the revving of an engine that for most people it immediately brings to mind images of cars. However, the word has not always been used in an automotive fashion. Back in the 1930s and 1940s it was not uncommon to find vroom (especially when used in triplicate) as a means of describing such disparate other sounds as exploding bombs, airplanes, and, oddly enough, the double bass.
Far back on the road there was the vroom, vroom, vroom! of exploding bombs.
— Liberty (Rye, NY), 10 Feb. 1940
”Vroom! Vroom! Vroom!” The big bass viol vibrated in the darkened school auditorium.
— The Arizona Daily Star (Tucson, AZ), 4 Jan. 1935
….to the trample of iron-shod heels the brow stage shook and the great plane’s vroom-vroom-vroom cut cleanly through the morning freshness.
— Detroit Free Press, 18 Aug. 1935
Since the 1960s the word, which is of imitative origin, has been primarily used to refer to cars that go fast.