To hastily clean your manhood in the basin of a pub’s toilets in preparation for a forthcoming sexual act with someone you’ve just met.
Dave hoped the bird he was giving a ride home to would give him a blowjob on the way so he had a gentleman's wash
by paella-munching fool February 04, 2006
The washing of ones genitals, usually in a pub toilet, before having casual sex after realising one hasn't bathed in a while.
Shortly before taking a girl into the car park for a good seeing to Jeremy went to the toilets for a Gentleman's Wash.
by Cleveland Steve March 19, 2009