Best definition
A term used to describe someone/something who has really annoyed you, who you would normally refer to out loud as

a Cunt but can’t because of your Boss or someone who might be offended and sack you. It’s a mixture of the childish term Willy to describe male gentials and the derogertary term Cunt to describe female gentials, and even though you may sound like a complete twat saying it out loud, because they won’t understand what you’ve said your less likely to get sacked! or punched.

OMG that Willicun of a stapler just made me bleed

Your such a Willicun, just get out

Louise “shut up you fuck”

Martin “bitch”

Louise “arsehole”

Martin “willicun”

Louise “wah?”

Martin “yeh!”