Something that is extremely amazing, shocking, crazy or mental (not in the psychological sense). 'Stone' being used to emphasise (as in very) the word 'radge', used in this context as incredible
Aye, that wee blonde piece goat er tits oot last night for the lads; it was stone radge man!
Used in Edinburgh slang as 'out of order' (not in the context of working state of a machine or object) or something that is below societies general moral acceptability.
You shouldnae uv chored that wee boys dinner money, that was pure shabby man