Simple past tense and past participle of tamper.(verb)
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Use "tampered" in a sentence
"But there's little in Confession's rich combination of personal memoir, historical exegesis and Buddhist primer that seems to warrant the degree of negative reactions it has inspired -- among the most heated of which is that he has "tampered" with scripture for his own ends."
"Your vehicle must not have a "tampered" emissions-control system."
"Made told MPs that the monkey "tampered" with the transformer and was electrocuted in the process."