evaded reparation or satifaction of a debt, sometimes by citing a technicality
that fucker welched on the Giants - Eagles (he bet they wouldn't cover the spread and they fucking did!)
Treated someone like the Welsh have been throughout history, that is ripped off. So the winner of a bet may recieve a welsh prize - nothing. From the outdated adjective welsh - meaning disadvantaged(in poverty and fate).
TheTruth : Yeah Dave did win the bet but I think he may be Welsh so it doesnt count.
Dave : I've been welched