When you take a nasty liquidy shit, usually caused by rancid meat from Wendys or Mcdonalds.
Lev took a Mcnasty which stunk up the joint.
by Chuck August 22, 2003
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Ordering a McDouble and a McChicken, then putting both patties between one set of buns, to create one nasty sandwich.
After the bar last night, I went and got a McNasty and 10 piece McNuggets.
by sirpilf March 15, 2010
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Usually a pretty girl, but also tends to be visably crazy. Usually spotted in North Beach; does not F*&@ with roofies as they are real and not a joke.
She is a real live person, that McNasty.
by Miss McNasty July 13, 2006
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it's where u have diarrhea, then u shit on a girls/guys chest and then wrap them in plastic wrap.
a guys girlfriend is sleeping and he gives her a McNasty. she wakes up and is covered in shit because she is wrapped up in plastic wrap
by dzman April 12, 2006
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-noun, overweight, ugly, disgusting McDonald's worker who you fuck; someone who nobody but YOU would have sex with
1. Dude, the drive-through lady is disgusting... That's a McNasty!

His first time was a McNasty, sucks to be him!
by MBA-BJS December 21, 2009
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1) derived from adding mc onto every word.
2) refers to a boyfriend who has weird habits, crab claws your chest or wont have sex with you even though he has no chance of getting laid.
3) someone who has bad acne and sort of looks like a gremlin because of it
1) The roadkill we just passed is mcnasty.
2) Mcnasty is coming over but we wont DO anything.
3) I got put on this cream because my face was mcnasty.
by Kalaniiii June 30, 2006
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