You describe something as regrettable when you think that it is bad and that it should not happen or have happened.
例句
...an investigation into what the army described as a regrettable incident...對軍方稱之為令人遺憾的事件的調查It is regrettable that strike leaders seem intent on spoiling holidays.遺憾的是罷工領導人似乎決意要破壞節日的氣氛。
英漢詞典釋義
adj.
令人遺憾的;使人懊悔的
His tiredness caused him to make a regrettable error.他由于疲勞而犯了個令人遺憾的錯誤。It is highly regrettable that the minister cannot be here in person.很遺憾，部長不能親自出席。
英英詞典釋義
Adjective
1. deserving regret;
"regrettable remarks""it's regrettable that she didn't go to college""it's too bad he had no feeling himself for church"