What is litter?

According to the law

The Environmental Protection Act 1970 defines litter as:

"litter" includes any solid or liquid domestic or commercial waste, refuse, debris or rubbish and, without limiting the generality of the above, includes any waste glass, metal, plastic, paper, fabric, wood, food, soil, sand, concrete or rocks, abandoned vehicles, abandoned vehicle parts and garden remnants and clippings, but does not include any gases, dust or smoke or any waste that is produced or emitted during, or as a result of, any of the normal operations of the mining, building or manufacturing industry or of any primary industry;

The Law section contains further information about the Environment Protection Act 1970 and the role of EPA Victoria. 

According to people

Research indicates that people perceive some types of litter on a scale of how harmful they think it is to the environment. Harmful or non-biodegradable - syringes, nappies and dog poo for instance - are viewed as unacceptable because they are undeniably harmful to humans and animals. Less harmful, biodegradable or edible - items that disappear quickly or thought to be edible by animals - seem more acceptable.

By definition though, litter is the presence materials in places they are not meant to be.