From The Art and Popular Culture Encyclopedia
Examples include municipal solid waste (household trash/refuse), hazardous waste, wastewater (such as sewage, which contains bodily wastes, or surface runoff), radioactive waste, and others. The term is often subjective (because waste to one person is not necessarily waste to another) and sometimes objectively inaccurate (for example, to send scrap metals to a landfill is to inaccurately classify them as waste, because they are recyclable). The terms can have various connotations, including pejorative tone (for example, "this spoiled food is nothing but waste now") or a squandering of potential (for example, "growing residential lawns in the desert is a waste of water").
Litter refers to waste disposed of improperly.