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Mayday, mayday, mayday! - This is a universal distress signal in a case of emergency. It's usually transmitted via radio.

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Pan-Pan -

"Pan-Pan" is used when there's a problem but the situation is not deemed serious enough and no lives are at risk, so using "Mayday" would be overkill.

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7500 -

You don't want your pilot to ever mention this number. The code 7500 means that the plane is being hijacked.

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Code Adam -

This one is used in several public places, including malls, airports, museums, and hospitals. It means that a child has gone missing.

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Time Check - If you're in a store and hear this one on the loudspeaker, leave immediately. It's a bomb scare.

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Inspector Sands or Mr Sand -

This signals an emergency situation such as a bomb threat or a fire. The code is used across the UK rail network, the London Underground, and even in theaters.

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Operation Rising Star -

This code is usually used in cruise ships. It means someone has died.

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Code Oscar or Mr Mob -

Shouting "Man overboard!" is probably not the best option in a crowded vessel. Instead, "oscar, oscar, oscar" is used.

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Code 10 - A "Code 10" can be issued by merchants if they suspect someone is committing credit card fraud. They can contact the card issuer and make a Code 10 authorization request.

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1488 - Used by white supremacists around the world, if you see this number in an email address, a t-shirt, or a tattoo, you'll know the person has a Neo-nazi ideology.

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London Underground cleaning codes -

There's a specific code for each situation. These include, code 1 for blood, code 2 for urine/feces, and code 3 for vomit.

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Code Red - A "Code Red" used in the context of a cruise line, means that there is a serious illness outbreak onboard.

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Mr Skylight/Alpha, Alpha, Alpha/Code Blue/Star Code - All these can be used to alert for a medical emergency aboard a cruise ship.

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PEBKAC - If you ever spot a tech guy referring to your case under this code, you'll know the problem is you. PEBKAC means Problem Exists Between Keyboard and Chair.

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Code 18 - If another tech guy says you have a "Code 18," then this means the problem is 18 inches from the screen. Yes, you again!

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ID-10T - You've probably figured this one out already.

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EEOC - Another tech code word to call you stupid. It stands for Equipment Exceeds Operator Capabilities.

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Treasured guest - This term is used by Disneyland employees to refer to a difficult customer.

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"I can haz PDF." -

Scientists use this code to ask for papers online. A social media post with a link to the research paper needed including this code is usually enough for someone to send them a copy.

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Echo, Echo, Echo - Prepare for collision if you hear this one aboard a cruise ship. Best case scenario, it's just a warning for high winds.

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Bravo, Bravo, Bravo - If you're aboard a cruise ship and hear this one, you'll know there's a fire or another serious incident.

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Code Bravo -

This a general security alert code used in airports.

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Protein spill -

If you happen to throw up at Disneyland, employees will refer to the incident as a "Protein spill" or a "Code v."

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Code Winnie -

This is the code used when kids pee in the swimming pool at Disneyland.

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U.S. police use a whole lot of 10s -

American police have a number of codes starting with number 10. Examples include 10-35 for a major crime alert, and 10-89 for a bomb threat.

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7600 -

In aviation, this code means that there is a problem with radio communications.

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Urban whitefish -

If you happen to listen to New York City Sanitation Department workers mentioning "urban whitefish," they're talking about used condoms. 

See also: Intriguing code names the Secret Service has given US Presidents and others

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