Some-one who thinks they know it all, but are generally just talking out of their backside.
When some-one lies and elaborates on certain subjects to make themselves look bigger/smarter, though usually ending up just looking like a fool.
Shervins can be male or female and are usually hated in their group of friends, regulary becoming the subjects of bitcing
She thinks by saying long words and talking about complicated matters and issues, she'll look big. But lets face it, she's a fucking twat who has no idea what she's talking about.