know one's onions

Definitions

Synonym of know one's stuff, to be knowledgeable about a given subject or task.

informal

Examples

“Joe really knows his onions when it comes to cooking.”

“Sam Tyler: Well, our first priority is to make⟳ sure the thieves don't strike⟳ again. It'll be tricky, 'cause these sorts of gangs rarely have⟳ just one target⟳ on the go. They've usually researched half a dozen possibilities, waiting for the most opportune circumstances on any of them. Harry Woolf: He knows his onions, this lad, eh? Gene Hunt: Oh, he's a right little smart-arse. So, what do you suggest⟳, Buddha?”

CEFR level