Slang term, commonly used in the North of England for plastic.
Particularly used in Teesside, Humberside and Yorkshire, as well as Merseyside
Across the UK, Manchester United fans are mainly said to live anywhere except Manchester. The common term for these fans in football circles are 'plastic mancs', or, as they are known in the North, Plaggy Mancs.
Plastic carrier bags are plaggy bags. Plastic macs become plaggy macs.
Something rubbish and can be used in most contexts, especially in a North East England accent, especially Middlesbrough
If somebody uses a rubbish comeback, you can say "how plaggy" and you automatically win the argument. also, if something is rubbish, e.g. "have you seen Mick's new car? it's so plaggy"