Definition of "souring" [sour•ing]

• Present participle of sour. (verb)
• Any sour apple. (noun)

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• "We see that here in the United States with what I call the souring of his presidency."
• "Meanwhile, Spain's 20% unemployment and persistent real-estate downturn has led to a rise in souring loans on banks 'balance sheets and lending growth is sluggish."
• "Reluctantly the demoness did, her expression souring as she parted with it."