Originating from Rugby Union, a Welsh win is winning through no identifiable skill or talent - or where all the factors that should contribute to a win were in favour of the other team. It's usually used in reference to were the winning person or team won for either an unclear reason or due to biased decisions by the ruling party.
"A bit of a Welsh win for Karen getting that job - the other applicant was far more qualified and performed much better at interview. I wonder who she's shagging?"
by OpeningLine February 27, 2021