Simple past tense and past participle of balloon.(verb)
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Use "ballooned" in a sentence
"The margin ballooned to 40-16 early in the second quarter."
"The verb ballooned is inspired, suggesting, as it does, puffed-up-ness and hot air; after all, it’s not the man’s worth that has expanded, but merely his sense of that worth (at least in the eyes of his observer)."
"The state originally estimated that it would cost only about $80,000 extra per retiree, but after legislators added all the union-demanded sweeteners, that price tag ballooned to $200,000."