1. Dobber , dobbing , dobbin' :- something 'big' - big headache, big penis, big idiot, big fool
1a. England:- A 'dobber' is a large marble (small glass coloured balls kids used to play with)
2. Australia, NZ (?):- to 'dob' someone in means to squeal on someone, to expose them, tell on them
I'll match my blue dobber against your medium stripey marble.