(intransitive, slang, informal, United States, almost always with about) To talk excessively, ignorantly and/or wrongly.
Don't keep flapping off about someone you don't know.
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Regional slang from around the English-speaking world — British, Australian, Irish, Caribbean, Nigerian, Filipino, AAVE, and the hyphenated-English dialects that make the internet sound local.
See all Regional & Other slang on Slangora.
Browse all slang words starting with F.