n. A day when one or more of your children does something bad ... very bad.
Why is Igor out on the window ledge mumbling about a hostage taking and some arrests?

Oh don't worry. He's just having a bad heir day.
by gnostic1 October 24, 2010
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Similar to a bad hair day, but instead of having nasty looking hair, the victim has nasty looking knees. May result in dryness, stubble from shaving, rashes and/or birthmarks.

Most often used by women.
Wow, look at all that stubble. I'm sure having a bad knee day today!
by Hazzat April 23, 2010
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1. When your ass just doesn't look good in anything , skirts , jeans , dresses. ANYTHING. Mainly affects women but gay and metrosexual men also suffer from it time to time.

2. When you don't want to be a nice guy and instead for just a day , turn into a badass. A bad ass day can starts from when you wake up to when you go to sleep , you may also have experience baddass dreams that night.
1. "My ass looked horrible yesterday . not even that weird Persian ghuy checked me out. It was the worst bad ass day"

2.

Oscar - "Was there any reason that you killed Mrs Porter's cat yesterday?"

Pete - "I was having a bad ass day"

Oscar - "Yeah I'm pretty sure the cops aren't going to take that into account".
by EthanStain October 3, 2013
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a bad day in general (from the belief that the appearance of one's hair is connected to how well the day goes)
I think you must be having a bad hair day.
by The Return of Light Joker July 14, 2010
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In Britain: the mood or feeling one experiences after having just filled his or her vehicle with £1.00+ per litre petrol (equivalent to $8.50+ per gallon of gasoline). Usually consists of a sense of great economic despair, impending doom, anger, frustration, depression and/or a combination of all the above
"I hate when those Americans complain about having a bad fuel day. I'm having a fucking bad fuel day!"
by Robert Pallas May 16, 2008
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A day on witch your strong sperm isn't being produced. All of the good stuffs been jerked away and now you're only left with bottom of the barrel seed. Children born on this day are twice as prone to developing mental retardation, lack of athletic ability, and/or ugliness.
"I got her pregnant on a bad sperm day, so he's practically not even my kid."
by 6J6W6 June 11, 2011
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A bad China day or BCD is a widely discussed phenomenon experienced by every non-China born human being living in the glorious motherland be they white, black or yellow as the rays of sunshine that radiated from Mao's asshole.

I don't actually have the time to list every frustrating experience you might encounter if you live in China. The internet doesn't work, the banks don't work, every product or appliance in your apartment will fall apart within a few weeks of purchase.

Sometimes, this all culminates on a single day and, yes, you lose your shit. It happens to the best of us. Telling someone having a BCD "Well, if you don't like it, go home!" is likely to result in having your larynx torn out, so don't do that.
A: Dude, I heard Greg is at the PCB having a tea-session and getting ready to have his ass deported! B: Yeah. He had one two many bad China days and went Falling Down on an illegally parked BMW.
by China Circle Jerk November 15, 2016
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