Simple past tense and past participle of flunk.(verb)
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Use "flunked" in a sentence
"Otherwise, it's enough that the idea flunked the "ick" test."
"(protection = productivity), cow bras are so obviously an attempt by one species to reshape another in its own image that the idea flunked the laugh test."
"The article doesn't say how many people got only one question wrong and how many people actually completely "flunked" the quiz (i.e. went 0/3)."