/ ˈplækɑːd; NAmE -kɑːrd/ noun
a large written or printed notice that is put in a public place or carried on a stick in a march :
They were carrying placards and banners demanding that he resign.
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WORD ORIGIN
late 15th cent. (denoting a warrant or licence): from Old French placquart , from plaquier to plaster, lay flat, from Middle Dutch placken .