An extension of the relaxed dress code for adults that prevails in some offices on Friday, "Casual Friday" for public-school students means either: going without underwear on Fridays, or (boys only) wearing a jockstrap instead of underwear.

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"What are you wearing to school for 'Casual Friday'"?

"That's for me to know and you to find out."

(speaker almost gets pantsed.)

"Okay, okay. I'm wearing my favorite orange jockstrap. How about you?"

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by al-in-chgo March 12, 2010
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1) wearing casual clothing (jeans, t-shirt) on a Friday.

2) a practice common with high schoolers where you don't wear underwear under your pants on Friday. It's really funny and really is only funny to the people that do it. But none the less, it's not as weird as you'd think.
Person: "Emily, are you doing Casual Friday today... because I noticed you're not wearing a skirt like usual."
Me: *laughs hysterically* do you even NEED to ask?
by Pretty Emily November 13, 2004
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In formal business environments, employees are allowed to wear business casual clothes instead of suits on this last day of the work week. Sometimes given a theme, it is intended to alleviate stress and bolster employee morale.

In smaller companies where business casual is worn every day, this day should be called just "Casual Friday" when lower-quality clothes are allowed.

When in doubt, it is better to overdress than to wear clothes too casual, so as not to be reprimanded by the suits.

formal > business formal > business casual > casual
Business casual: Sweater, collar without a necktie, polo, vendor swag, blouse, black/brown/navy/gray trousers, pressed khakis.

Casual: Dockers, denim jeans, shorts, t-shirts, linen.
by Coell July 6, 2005
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The term used by places of buisiness that allow the employees a slackening of the dress code on the final day of the work week. Commonly known as "Biz Cas Fri". Well, not really.
"Oh, how I love to wear unique-colored pants and a belt full of metal squares rather than just plain khakis on BUSINESS CASUAL FRIDAY."
by Kaleb Matthews January 13, 2006
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When one person, or a small group of people, abuse or break a code, rule, or law, which in turn ruins privileges for everyone, both directly and indirectly involved. Shoplifting, unnecessary texting and phone calls while driving, and people making bombs out of their fucking shoes on airplanes cause the rest of us to suffer on a daily basis from The ‘Casual Friday’ Effect.
Example 1: From The Office episode “Casual Fridays.”

Toby: “Casual Fridays are canceled… There’s not a single appropriate outfit in this whole (office) except mine, quite honestly.”

Toby canceled Casual Fridays after Meredith wore a dress that was too small, exposing her breast (and then some) when Toby suggested ‘pulling it down a touch.’

Example 2:

Girlfriend: “What took you so long?”
Boyfriend: “Ugh. I had to buy refills for my MACH3 Turbo.”
Girlfriend: “I know, right? I usually have to wait about fifteen minutes for someone to unlock the case at Target when I need more Britney Spears’ Curious. Damn The 'Casual Friday' Effect!”
by marshmallowgirl May 1, 2009
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The day when peolpe at the office wear free polo shirts they got from various software companies.
by SMD August 22, 2004
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The opposite of casual Friday with regards to clothing attire. Business casual in sense of the traditional carefree jeans and a T-shirt outfit.
I walked into class looking like I just came from an interview but I thought to myself no it's just non casual Friday.
by Business casual guy September 17, 2010
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