Absolute plank and a dickhead

To Fionn is to eat large quantities of fatty foods or unhealthy food from a fast food outlet (such as McDonalds). The general result is an obese person or a fat ass (most commonly used in reference to males). If you were Fionning, you would be eating the food.
It can be used in context as a noun and as a verb.

Some ginger fella who thinks he’s unreal at hurling but is shit and is bazzas bitch. He plays for boden which are by far the worst team in Dublin. He has a red piece of broccoli on his head that looks shite. He sometimes tends to put on a nacker accent despite him being from Knocklyon. He also is sexually attracted to children and kissed a fifth classer while he was in second year. An all round dodgy fella if u ask me.

A Fionn is a good looking boy with an amazing personality. He will get all the beaurs and is a kind hearted guy. He has loads of friends and is an overall unit

A genius who will delete your discord server if you mess with him.