Simple past tense and past participle of swell.(verb)
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Use "swelled" in a sentence
"Since Costolo's arrival, Twitter has moved into larger offices in San Francisco to accommodate a payroll that has swelled from a few dozen people to about 300 employees."
"Nor did she notice the tiny drop of blood that swelled from the tiny hole it left in her flesh."
"Sometimes her feet swelled from the walk to her seat, but she didn't have time to care."