In competitive angling it used to be fishing with mono .40 and below and leader lenght of no longer than 3m. There is no more official light tackle. I think is now more a peronal thing. I will say fishing with braid 25lbs and lighter will be considered as light tackle and mono still .40 and below. I am talking about Shore Angling not other facets.
Most .40 mono is about 25lbs.