or blow·by


noun, plural blow-bies. Automotive.

leakage of the air-fuel mixture or of combustion gases between a piston and the cylinder wall into the crankcase of an automobile.
a device, fitted to a crankcase, for conducting such gases back to the cylinders for combustion.

Origin of blow-by

First recorded in 1930–35; noun use of verb phrase blow by Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for blow by



the leakage of gas past the piston of an engine at maximum pressure
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012