Top definition
When you go to a party, get super wasted, and find a hot chick to bang. however, you don't realize the "hot chick" last night, was your sister. buts it's ok because you used a rubber.
last night Travis went to a party and found a bomb ass chick who said her name was Stephanie. I can't wait til he realizes he guenther'ed his sister. She same Stephanie that is his sister. whom he has lived with his entire life, and who's bedroom is 4 feet from his.
by delivery boyy! February 03, 2010
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2
a person or group of persons that experience unfortunate events due to the "force unknown".
or:

the first born offspring of the blue spotted african llama.
Dude, today has been such a GUENTHER!

or:

Your as ugly as a guenther.
by BryceBerryManne October 20, 2007
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3
Doing a 'Guenther' - finding any excuse to avoid hanging out with your mates. Examples include scweffing with wife/girlfriend and playing golf with father-in-law.
Is Jon coming this weekend? Nah, he's pulled a Guenther.
by Whiskycam April 01, 2017
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