informal to fail to do what you have promised to do
They'd agreed to pay half the costs, but they welched on the deal at the last minute.
phrasewelch on welch on sth/sb not passive to not do something that you have promised to do for someone, especially to not pay them money that you promised them: Former clients are accusing them of welching on deals they had agreed on the telephone.■ SIMILAR TO: rat on informal