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 when it comes to corporate accounting.
See also: know, stuff
Farlex Dictionary of Idioms.

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
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • know (one's) stuff
  • know one's stuff
  • know your stuff
  • know your onions
  • know (one's) onions
  • know about
  • know about (someone or something)
  • have a good command of
  • have a good command of (something)
  • triple threat
References in periodicals archive
I was informed by an old school mentality, which is -- you want to preserve your career and your success and your productivity, and there are people in the world who don't like you, and they don't like that you date girls, and they don't like that you don't identify as a quote unquote 'lesbian,' but you also don't identify as a quote unquote 'heterosexual.' And people like to know stuff, so what the f**k are you?" she asked.A
She continued, "I was informed by an old school mentality, which is -- you want to preserve your career, success and productivity, and there are people in the world who don't like you, they don't like you, date girls, and they don't like that you don't identify as a 'lesbian,' but you also don't identify as a 'heterosexual.' And people like to know stuff, so what the f*** are you?'"
You know, at times it can be a relief to just not know stuff. It's a lot less work for me to just confess "I have no idea." My adult children and grandchildren now enjoy teaching me what they know and we all have fun in learning new things together.
"You know stuff like this happens but it's frightening when it happens on your doorstep.
So let's accept for a moment that you know stuff has to go.
I feel at a disadvantage when I meet people because they know stuff about me but I don't know anything about them.
"[A writer asked,] 'Do you wanna know stuff? Do you not?' I said, 'Oh, I don't know.
For those born after the year 2000 and think they know stuff, let me give school you.
Two guys who really know stuff, developed this hammer/sear and bushing set, and as much as I hate to say things like this, I do think it's really going to revolutionize things for the 1911 set.
My stylist Stuart (ok, who am I kidding, my mate who once worked in Prada so he must know stuff) suggested a sheer fabric would be most complimentary, something like chiffon.
Grealish added: "The manager and coaching staff will know stuff like that.
She heard about it from a friend and colleague who posted about Women Also Know Stuff on social media, and finds it affirming to scroll through the lists of women scholars.
I know stuff. I get things right on University Challenge.
I write the children a letter and say I'm totally honoured, but unqualified for the role, but I'll talk to them when they're 16 and that I know stuff about their parents, so when they're really annoying them, they can come to me and I'll dish the dirt!" MY HUSBAND "LUDO and I have been together since I was 20, and the contented, more self-assured way I feel now is probably 80% down to the fact that I've had such a stable and fulfilling relationship.
I PUT them into two categories - those that are very plausible and probably could sell you anything on the shopping channels and those who just know stuff.