"There is a myriad of reasons a relationship is toxic. So I don't believe there is a definition of one, bar one that isn't good for your own wellbeing "
A relationship whereby one or more people involved are making the others feel unhappy, unwanted or abused in some way. Of course that’s just one definition. So many fucking assholes out there.
A toxic relationship is when essentials like love, respect, sex are withheld and it is all about manipulation, control and power.
I have been through one on the receiving side and it could be quite damaging and might leave permanent mental scars.