If you look the word up in a dictionary you will get an answer involving anti-social and perhaps criminal behaviour, lack of conscience and a tendency not to form real relationships with people.

A major difficulty for psychologists is deciding the difference between psychopathy and sociopathy. There is no 100% agreement, but the usual difference is thought to be that whereas a psychopath is without any conscience or empathy at all, a sociopath may have empathetic feelings for a selected group of people.

You can find scores of online tests claiming to identify the traits of a sociopath, but none of these is authoritative. Generally you are looking at an inability to feel remorse or accept criticism, a way of using others as things rather than relating to them, and a tendency to switch character or beliefs according to your self-interest. You can find some of the commonly identified traits here.