know stuff

know (one's) stuff

To be very knowledgeable or skilled in some area. I think Nicole is our best candidate for the job—she really knows her stuff about corporate accounting.
See also: know, stuff

know one's stuff

 and know one's onions
to know what one is expected to know. I know my stuff. I can do my job. She can't handle the assignment. She doesn't know her onions.
See also: know, stuff
References in periodicals archive ?
I need to know stuff about every single player: injuries, statistics, manager changes, everything.
He said: "He would be one of my favourites, and Arthur C Clarke - people who really know stuff and can make science really interesting.
You know stuff and ou know stuff and Y what you don't know, you know what you don't know, you know how to find it out.
I SHOULD know stuff about Syria - the students of King's Academy do, but I don't.
The really great quizzers know stuff they're not interested in.
Your body hurts and you can't communicate with anyone, and you think you know stuff before you know it and your parents are idiots and they're embarrassing.
Modern technology means they know stuff about you, what you have bought from them previously, and know which words and phrases could trigger off a potential sale.
His mother who was there with him all the time, she started picking up on it, you know stuff was missing, money here, stuff like that.
The Holiday Inn Express brand understands that when you stay smart, you know stuff, and so the brand wants to give consumers the chance to share their smarts with others through popular social media outlets.
He knows I'm one of the captains, and he'll let me know stuff after the game I need to relay to the team.
10 Reasons why Dubai sucks K Shahid's profile is simple: "I know stuff.
I know stuff I don't like and I know when it is going to sell like hotcakes.
And once you've been in the business for a long time, people kind of know stuff about your life.