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.在這個市場里，一些人可能根本不講道德原則，非常令人厭惡。...the unprincipled behaviour of the prosecutor's office during the crisis.在危機期間檢察院的不道德行為
英漢詞典釋義
adj.
不道德的,肆無忌憚的,不誠實的
an unprincipled person肆無忌憚的人
英英詞典釋義
Adjective
1. lacking principles or moral scruples;
"freedom from coarse unprincipled calumny"- A.E.Stevenson