Simple past tense and past participle of flat.(verb)
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Use "flatted" in a sentence
"On the other hand, in order to lower a tone, the letter representing it is "flatted," and F is called _Fes_,"
"They would later discover, after Bewley flatted about halfway to Mumbai, that no one had any extra wheels so they quickly had to replace one of the tubulars."
"Then Miller flatted at the top of the course, gapping Smith and giving Annis the chance she needed."