Simple past tense and past participle of amass.(verb)
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Use "amassed" in a sentence
"The art collection Mr. Shorenstein amassed with his late wife, Phyllis, included Gustave Caillebotte 's cheery river view from 1882, "The Seine at Argenteuil.""
"Wisconsin amassed 311 yards and a 17-0 lead in the first half, leaving little doubt that Alvarez would get to celebrate another big win."
"While all these folks may be really wealthy, in reality the wealth they have amassed is but a small percentage of the wealth and value that they created."