When one slams their penis in a door, and then screams and runs from the pain, elongating their penis. The act is also done by Manjo players looking to finetune their instrument
Henry carefully did the slinkydinky in order to fine tune his manjo
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).