During sex, when the penis fully exits the vagina and upon attempted reentry, bounces off the labia and or clitoris; potentially causing erectile disfunction.
I was unable to fully please her because I ricoflected my dick and became instantly flaccid.
Typically invoked by governmental officials during sworn testimony to the U.S. Congress to deny potentially damaging -- politically and/or criminally -- behavior.
From the 1994 film "Clear and Present Danger" starring Harrison Ford:
Jack Ryan: Who authorized this?
Robert Ritter: I'm sure they'll ask you that.
Jack Ryan: Who authorized it?
Robert Ritter: I have no recollection, Senator