A flaccid penis, usually very soft and small. Plen is not a sexual term, rather a term of endearment.
Plens can be considered cute under certain circumstances.
"Did you hurt your plen again?" "- yes, my plenis got caught in the door."
Cailan Plen is a diplomatic masterpiece of a human being. He is for the people and will lead your country to greatness. If you see Cailan Plen he will inspire you to do greatness and make someones day.