Costin is a person who has a very large penis ( from 18 to 27 centimeters) and they have a really good sense of humor.
They are also a really good person to have in your group.

A person with a very large penis usually 37-55 inch long

guy behind me.

to rush headlong into a suicidal career spin, then burn every bridge in sight including the one you're standing on, whilst providing some fleeting entertainment to your colleagues.

The man, the myth, Da wig! A cool dude who drinks way to many energy drinks, has way to much energy, and has a “Costin”