To "black flag".

Meaning to make a bet, and lose it. Then not follow through with the consequences.
YOU: "I'll make a bet that Carlton suck and miss the 8, loser has to suck Suzis penis."

BlackFlag: "Carlton will win the premiership you douche, i'll take your bet"

Carlton go on to stink up the entire competition, blackflag loses the bet, and ignores that the bet was ever placed. Making him a dirty welch and the lowest form of life in the universe.
by Blissid April 28, 2010
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to avoid doing something you have promised to do, especially not to pay a debt
Marty got his thumbs broken by Vito after he welched on a gambling debt.
by contractorpeon March 3, 2005
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To welch. To go back on your word. A highly derogatory word made popular through the be-mag messageboard crew in response to wirolla's act of cowardice.
Wirolla had two options; tits or GTFO. He welched, he chose the second option.
by gatsby. September 5, 2008
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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!)
by danielwebster May 19, 2007
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To shove Welch’s fruit snacks up someone’s ass.
Bro last night I welched this bitch than ate the booty like groceries.
by Fruit Snacks August 15, 2018
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Dumb ass bitch who never does what they say they're going to do.
There's a welch on the phone who said she'll be here at three, but we all know she's not going to show up today.
by Squeaky_lil_b January 22, 2016
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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 From the outdated adjective welsh - meaning disadvantaged(in poverty and fate).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
by anothermadeupname April 20, 2010
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