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2.
Originating from the Gangstarr song "Moment of Truth" a Dennehy moment is a point in time when you or your associates realize the girl you hooked up with is grotesque/ugly.
When I remembered that Rosie O'Donnell gave me a handjob last night, I knew it would be a Dennehy moment for the rest of my life.
After I heard Ian McCulloch, the famous DJ, hooed up with Amy Poehler at Lindsay Lohan's condo, I knew it would be a Dennehy moment for the rest of his life.
by MrBigDef March 30, 2009
 
1.
A point in time when you or your associates recognize the girl you hooked up with is grotesque and/or overweight.
After I remembered that Rosie O'Donnell gave me a handjob last night, I knew it would be a Dennehy moment for the rest of my life.
Bro, Did I just see you with Amy Poehler back at Lindsey Lohan's house? Denehy moment.
by 420 69 Hockey March 30, 2009