An imaginary creature that lives under one's floorboards and arises at night to tickle the scrotums of insecure thirteen year old boys who someday dream of becoming playwrights.
Poor Davey McDoodlestein hasn't slept in five days, and I'll tell you why - it's all because of that smelly little Shimbly Wingbarker that lives in his closet. I told him to get that thing taken care of, I did, but you know these kids today think that they know everything...
Couples usually write them on unsuspecting places so the other person can find them, thus showing them how much they love the other.
Once on person finds "shmily" somewhere, they will write "shmily" somewhere, and wait for the other person to find it.
The pattern goes on and on.
Vivian opened her wallet to find a slip of paper with "shmily" written on it. To reciprocate, she hid a piece of paper with "shmily" in Michael's pants drawer, waiting for him to find it.