vapour pressure n (General Physics) physics the pressure exerted by a vapour. The saturated vapour pressure is that exerted by a vapour in equilibrium with its solid or liquid phase at a particular temperature Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014