A behavioural attribute that is the extent to which it results in addiction in people who engage in it.
We often refer to 'addictiveness' of drugs, but this is imprecise and inaccurate because it is the behaviour of ingesting a particular drug formulation in a particular way to which people become addicted. For example, people talk about nicotine having high addictiveness, but it is particular behaviours that involve ingesting nicotine (e.g. cigarette smoking) that are addictive while others (e.g. putting on a nicotine transdermal patch) are not.