Bulky waste refers to those items in your house that are kept for disposal but are too big to fit the regular garbage bin and also cannot be sold to anyone or donated as charity.
They can be items like old furniture or appliances which are no longer in use such as fridge, dishwasher, etc. which fall into the category of clean bulky junk.
It also includes items, which are called dirty junk like home improvement waste, such as tiles, rubble, etc. and kitchen units, doors, windows, bathroom...