Definition of what's what in US English:

what's what

phrase

informal
  • What is useful or important.

    ‘I'll teach her what's what’
    • ‘So I've been doing this trial-and-error experiment to find out what's what.’
    • ‘The Bureau of Alcohol, Tobacco and Firearms wants to know what's what.’
    • ‘Your mom might get what's what if you fill her in.’
    • ‘De Niro's gravelly voice tells Scorsese: ‘I look you in the eye and tell you what's what.’’
    • ‘I am having a meeting with the council and the police before planning permission goes through to see what's what, and then go from there.’
    • ‘Call back at four this afternoon and we'll tell you what's what.’
    • ‘For those new to computers, our comprehensive Computer Beginners area will cut through the junk, jargon and technology to tell you what's what in plain English.’
    • ‘I find I'm losing track, though, of who's who and what's what.’
    • ‘Yes, you guessed it - the subject is the upcoming election, and the political scientists think they know what's what.’
    • ‘And as for the rumbustious cattle, typically I (dog free) found that a period gazing into their big brown eyes soon brought boredom to both parties and one can roll on without them charging along to see what's what.’
    the facts, the details, the particulars, the picture, how things stand, the lie of the land, how the land lies, the case
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