I have heard therapists refer to as people or relationships as "toxic." You mother is toxic. This relationship is toxic. Your boss is toxic. Etc.

I've read it in psych books too. People don't use the term consistently either. I can't quite understand if it refers to people with certain severe forms of personality disorders (which?), to very manipulative people, to very damaging abuse, etc.

I don't like the term because it's not specific but sounds scary. Anybody know what it means exactly?