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Typically used in schools. When a teacher or supervisor's not around and the student aren't doing what they're supposed to (i.e. Using their device, fighting, etc), a student that first notices a teacher is coming to their classroom yells to the class, "NINETY!". Which is a code word meaning a teacher is coming. The students can then quickly get back to what they're supposed to do.
Jack: Yo, Ms. Kira's coming back!
Sally: NINETY! HOT NINETY
*class scrambles back to do their work*
Ms. Kira: I'm back! Everyone doing what they're supposed to?
Class: Yes Ms. Kira
Ms. Kira: Good job!

Ninety-Ninety Rule 

A rule for tracking computer programming development time.

The full statement of the rule is, "The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time."

The rule simultaneously emphasizes two important points in software development. The first is that for almost any product, most of the development time will be used on relatively small but difficult sections of the code. The second is that the first point often leads to extremely optimistic project schedules.

The ultimate lesson to learn from this rule is that the amount of the project that is completed is NOT tied to the amount of code completed, and that substituting one for the other can be disastrous.

The ninety-ninety rule is often mistaken for a typo, with users assuming that the first 90% of code should correspond to the first 10% of time; while this is logically correct, it is NOT the original aphorism.
A: "This stupid ten-line function is somehow crashing on one out of every 100 calls and nobody has a clue how to fix it. We've got a week left in the schedule and haven't even fully identified the problem."

B: "Ninety-Ninety Rule. You should have expected from the start that something like this would come up."

Ninety-Niners 

Lab slang describing a group of quantum-computing researchers that has prepared a Bell-state using a two-qubit entangling gate with a fidelity equal or higher than 99 %.
German lab rat: The Raman laser is not locking again.
Indian lab rat: Hold my beer, I’m tweaking the PID parameters.
Spanish lab rat: Come on guys, without sideband-cooling we’re not Ninety-Niners anymore!
Ninety-Niners by Hyonoko September 28, 2021

Ninety-sixer

A sexual position where a man and a woman lie back to back, with their heads at opposite ends of the bed. With none of their sexual organs are even remotely lined up.

It is favoured by people with strong religious beliefs.
Yo man last week at bible camp I had a hot Ninety-sixer with Rach. Had to go to confession afterwards, but Geez it was worth it.

I hope Jesus wasn't watching.

Ninety-percent water, ten-percent vinegar 

n.) a douche

adj.) the condition of being a douche.
Karl is ninety-percent water, ten-percent vinegar. As a matter of fact, he is the biggest douche I know.

Ninety-Niner

A person who moved out to San Francisco during the Internet gold rush at the turn of the 21st century, roughly in the year 1999.

It is a play on the term "Forty-Niners," which refers to people who moved out to San Francisco during the gold rush around the year 1849.
Yes, I did come to San Francisco in August of 1999 to work for pets.com, but I find the term "ninety-niner" offensive.
Ninety-Niner by NYCDavid July 23, 2012
More from Urban Dictionary

square grouper

Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."
square grouper by slipsheet November 6, 2004
Word of the Day on October 7, 2026
A girl who does ballet and only talks about ballet. Her schedule is filled with dance classes which does not allow her to do any other activity.
"Hey, do you know that girl Sally?"

"Yeah, she's kind of annoying. All she ever talks about it ballet."

"Wow, what a Bunhead."

"Hey Sally, you want to hang out this weekend?"
"I can't, I have dance."
"You're such a Bunhead."

"Yeah... I know."
Bunhead by Jen00 October 24, 2014
Word of the Day on October 6, 2026

trucker's tan 

A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.
I had a trucker's tan after driving for 10 straight hours on a sunny day.
Word of the Day on October 5, 2026
The phenomenon where adults salivate at children's toys
Every time I walk into the toy aisle, I catch myself kidulting over the latest action figures and LEGO sets!
kidulting by Emotional Cruiser October 12, 2025
Word of the Day on October 4, 2026
British slang for a scientist or technical expert, esp . when the speaker is not certain of the expert’s specific field of study. Not necessarily derogatory, but typically used by persons without a technical background. In the US, the equivalent would be “egghead”, “squint”, or “geek.”

Origin of the word is unknown. Started sometime in World War 2. Given the typical evolution of British slang, could easily have started because what these experts did was confusing or “baffling” to the common person.
According to the boffins downstairs, the murderer used a serrated blade.
Boffin by Agnon February 11, 2023
Word of the Day on October 3, 2026
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