A Wingle Penny is a One Cent Piece that has fallen on the ground. It doesn't matter if it is heads or tails, it must be picked up.
To negate the usual bad luck of picking up a penny that is on tails, you must proclaim "Wingle Penny", then flip it to the heads side. Then it is safe to pick up and become part of your collection.
All Wingle Pennies must be spent, so they can re-enter circulation and hopefully become Wingle Pennies again.
If you find a penny on the ground and think that it is a Wingle Penny and leave it, you will then gain bad luck for the rest of the day.
The "Wingle" is a term that can also be applied to other coins that are found lying on the ground, however most usually it will be the One Cent.
Also, fries that are left at the bottom of a fast food bag, eg McDonalds fries, are Wingle Fries and are to be eaten instantly.