know your onions
US /noʊ jʊər ˈʌnjənz/
UK /noʊ jʊər ˈʌnjənz/
1.
很懂行, 精通
to be very knowledgeable about a particular subject or field
:
•
You can trust her advice; she really knows her onions when it comes to finance.
你可以相信她的建议；她在金融方面确实很懂行。
•
The mechanic quickly identified the problem, proving he really knew his onions.
机械师很快就发现了问题，证明他确实很懂行。