Wiktionary
brrm
interj. (context especially used by children English) The sound of a car engine.
Usage examples of "brrm".
Item second, buy that Porsche he'd dreamed of ever since the words brrm brrm had crossed his lips.
There is nothing that can be in our way, for this is the Cat, that laughs at barriers, and purrs brrm-brrm.
And Nym was still clutching the wheel, his eyes manic and his snout still contorted in a wild grin, making brrm-brmmm noises.