If you describe a person or their actions as unprincipled, you are criticizing them for their lack of moral principles and because they do things which are immoral or dishonest.
例句
It is a market where people can be very unprincipled and unpleasant.在这个市场里，一些人可能根本不讲道德原则，非常令人厌恶。...the unprincipled behaviour of the prosecutor's office during the crisis.在危机期间检察院的不道德行为
英汉词典释义
adj.
不道德的,肆无忌惮的,不诚实的
an unprincipled person肆无忌惮的人
英英词典释义
Adjective
1. lacking principles or moral scruples;
"freedom from coarse unprincipled calumny"- A.E.Stevenson