Heroin/ˈherəʊɪn/ Definition 1 of 1Pro Tip 1/3Illegality Heroin is illegal in most countries and referencing it might imply criminal activity. Being caught with heroin can lead to arrest. Pro Tip 2/3Negative Connotation The word 'heroin' often has a negative connotation, associated with addiction and crime. He battled heroin addiction for years. Pro Tip 3/3Health Hazard Heroin is a health risk, causing harm and sometimes death when misused. Heroin overdoses have become a public health crisis.