INSTANT FLACIDITY 

When your dong is suddenly gone because you were trying to have sex with your sister then your girlfriend walked in. (That word is only a valid word in cases exactly like this)

I was tryna fuck my sister, but bae walked in and my dick got scared so it let out a loud shout saying "INSTANT FLACIDITY!!!" Which of course activated the power to retract immediately so as to flee a dangerous situation

INSTANT FLACIDITY by YouDontKnoMe_ September 10, 2019

Instant Flaccidity 

An adjective describing a member of the opposite sex that is so thoroughly repulsive that you couldn't and wouldn't be able to have sex with them under any circumstances.

The new supervisor at work is ok, but once she opened her mouth you knew it was instant flaccidity.

Instant Flaccidity by RocketManFL January 15, 2007