Simple past tense and past participle of thrash.(verb)
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Use "thrashed" in a sentence
"Right now it's pretty dry and thrashed from the stripping treatment, but I have expensive shampoo and conditioner, and the brutal hairdresser assured me that with patience and continued use my hair would work its way back to normal."
"Winds up to 84 mph and blowing rain thrashed the downtown area."
"The EFSF will eventually have the capacity to spend €440bn under the terms thrashed out by eurozone leaders last month."