1. A girl who has had too many intoxicants and has lost her grip on reality.
2. A bitch, but you can't help but be affectionate about her.
3. One of your guy mates who has done too much weird gay shit to be a wasteman.
'Katie Price is a fucking wastepoon.'
'Shit son, that bird over there is literally wastepooned.'
'Ah, aren't you my lovely little wastepoon :-).'