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Opposite Day 

Rooted in playground tradition. A fictional holiday, in which everything you do or say means exactly the opposite. Often used at the end of a sentence to negate what you just said.
"You look nice.... on Opposite Day!"
Opposite Day by Dr. Michael yates January 17, 2005
Word of the Day on July 7, 2005

Opposite Day 

A fake holiday where you do exactly the opposite of everything.

Obviously is wrong in itself, because if everything is opposite, than opposite day cannot exist. And no, it can't go the other way, obviously, since there is no opposite day.

Try this logic with 4th graders.
4th Grader: IT'S OPPOSITE DAAAYZORZ!!
Smart Person: If it's opposite day, than that means it's NOT opposite day, dumbass.
4th Grader: OMG WTF YOU MEEN NERRRD! HAHAIDIOT.
Opposite Day by A guy. March 31, 2005

Opposite Day 

Opposite Day is a fun "game" played on another. You never know when this day takes place, but when it does, everything you say has the opposite meaning of what it would on a normal day. The quest is on to figure out when this day actually happens, so you can safeguard yourself from its horrors.
H-bird: Imma snaxe you, you snaxe
*readies sticky hand*
Snaxe: Haha, It'sssss Opposite Day today, you can't snaxe me!
H-bird: Gosh Dangit.
Opposite Day by Hecretary Bird July 26, 2020

Opposite Day 

A day where everything you say means the opposite of what it normally would. Kinda juvenile, but its fun too.
OMG It's opposite day, so I'm gay, Tony Blair is a fascinating and compelling leader, and my g/f is flat...

Not Opposite Day 

See opposite day.

1. A term used to describe that it is, in fact, opposite day which can only be used on opposite day. The

"not" is usually over-emphasized, and the term usually follows a wink, nudge or other non-verbal que that the speaker means the opposite.
The rational behind this use of the term is that if it is Opposite Day, then the correct way of proclaiming that it's Opposite Day, is by actually proclaiming how it isn't Opposite Day.
This is the most commonly used form of the phrase.

2. A term that is used to genuinely describe how it is not opposite day. This use of the phrase is usually used by those that do not plan on partaking in Opposite Day, and therefor will mention that it's actually "not Opposite Day" when people say it is (or on Opposite Day, isn't). This usually does not work, as the pro-Opposite Day party acts as if the other party is in cahoots with them, not shutting them down.
1. "Guess what today ISN'T. Today is NOT Opposite Day!" *wink* *nudge*

2. "Stop saying that it's opposite day, because it's not Opposite Day." ... "That's not what I meant, I'm not agreeing with you in Opposite language, I'm trying to tell you that it isn't opposite day!" ... "UGH!"
Not Opposite Day by ItsGordie February 26, 2010

Opposite Day 

Opposite Day (n): Today is opposite day, so you must say no for yes and yes for no. It's also the only day you go back and stay back.

Opposite Day is the day where everything is reversed. But if opposite day is opposite day then shouldn't opposite day be opposite to opposite day? Meaning that everything that is opposite is opposite because opposite is opposite of opposite
2nd Grader: Hey student(teacher in this case), did you know today is opposite day.
Teacher: No, I didn't. But if today is opposite day little Timmy, shouldn't it be opposite?
2nd Grader: Wtf does that say?
Opposite Day by SenshiButaniku April 25, 2019
More from Urban Dictionary

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

Pee Calculus

When you have to pee in a movie but don’t want to miss anything, and must do the following mental equation: will the amount I have to pee cause enough discomfort to diminish my attention capacity for the remainder of the movie to an extent which is greater than the amount of the movie I would miss by making a mad dash to the restroom.
I saw Satantango last night, wonderful film but by the 5th hour I had to start doing pee calculus.
Pee Calculus by anorlondo October 1, 2026
Word of the Day on October 2, 2026
Literally "dirty" pronounced with a West Indian accent. Can also have a positive connotation, for example Sean Paul's album title "Dutty Rock".
"The girl is pretty but she corrupt and dutty!"

or, in a positive usage:

"Booya! That freestyle was dutty!"
Dutty by J Hall April 3, 2003
Word of the Day on October 1, 2026
korean word for madam, older woman
Ajumma wait a moment
Ajumma by aintnotinbutnice July 5, 2009
Word of the Day on September 30, 2026
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