The phrase essentially means, "What is your location?" or "Identify your position," but is a corrupted phrase from the original "10-20" used by United States law enforcement to verbally encode their radio transmissions to that non-police listeners would not easily discover police operations, as well as to communicate quicker and more efficiently by standardizing frequently used phrases.

These verbally-coded messages were called "10 codes", of which "10-20" stood for "Identify your position," or "Where are you?" originally. Other such codes include "10-7" meaning the officer was busy such as with a traffic pull-over, "10-8" meaning that the officer was back on patrol such as from having just written a citation, the popular "10-4" as an affirmative, "10-10" as a negative and "10-22" to disregard a previous transmission have only seen light integration into common use. It was not uncommon for a city to have its own set of particular 10-codes for other phrases frequently used particular to that locale.

This code-phrasing is similar in design to Amateur Radio Operators' (which require an FCC license) use of Q-signals, such as QTH ("What is your location") and QSL ("affirmative/understood") used to reduce the time needed to transmit and interpret a Morse-code transmission.
A: What's taking so long?
B: I'm at a red light that won't turn green even though there's no cross-traffic.
A: What's your 20?
B: Avenue F and Kingston.

A: QSL.
by thehomeland January 20, 2012
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This voice-communication alternative to "where are you?" derives from the police 10-codes, no longer used in most jurisdictions but nearly-standard in the U.S. from the 1940's until federal agencies discouraged them in the 21st century. "10-20" meant "What's your location?" or "My location is..." depending on the context. Ten-codes peaked in public awareness in the 1970's when the hit song "Convoy" brought citizens-band use of "10-4" to a period of widespread recognition.
The raw rookie cop had noticed that most police on duty substituted a different phrase rather than using the ten-codes he'd been taught in the Academy. He transmitted "where's your 20?" to his partner because he'd forgotten other cops usually said "what's your 20?". His veteran partner responded, "In my wallet with my five and two ones".
by Houndawg January 20, 2012
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Johnny,i'm going to the party , what's your 20?

My 20 is Baker Street.
by Jessy Wilde October 18, 2006
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What you ask a person when you want to know where they're at sexually.
Guy: Girl, you fine AF
Girl: Thanks
Guy: What's your 20?
by the one with the stuff September 6, 2015
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As in "What's your location?" Truckers ask other truckers this question in an attempt to triangulate smokey's location.
Bud says, "Jed, you might wanna mind your meter, the bear is round the bend."

Jed says, "that's a 10-4, whats your 20"?

Bud: marker 27.

Jed: I got my eyes on.

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often shortened to: "what's your 20?" or just 20? when texting
by Mr Major July 2, 2008
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