something that is old, dirty, a little over-used, messy or otherwise slightly over-loved! can aslo describe a person in an ironic way see example 2 below!
EXAMPLE 1
person 1:that table is old, like an antique person 2:yes it's quite shabby
EXAMPLE 2
person 1; person 2 you are not too shabby(meaning you are not too bad)
person 2: that shall be our word and we will make it cool, shabby
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.