careless
单词辨析：
指在做某事时精力不集中的，因而造成错误、损失等。
A careless driver is a killer.
一个粗心大意的司机就是一个杀手。
He is careless about his work.
他对工作很马虎。
指某人经常丢三落四的，也许因为精力不集中，也许是由健忘症引起的。
The absent-minded professor is always losing his books.
这位健忘的教授老是丢书。
She had an absent-minded look on her face.
她脸上露出心不在焉的神色。
指对某事掉以轻心，或茫然地陷入沉思且未注意到周围的情况或活动的，通常作表语，常后接介词 of。
He rode on, heedless of danger.
他不理会危险，继续骑马前行。
She is heedless of the noises outside the window.
她没有注意到窗外的嘈杂声。
指行事鲁莽、不计后果的，作表语时常可与 heedless 换用。
a reckless teenager
一位毛手毛脚的少年
be reckless of consequences
不顾后果
He is a reckless driver.
他是个鲁莽的司机。
He is reckless/heedless of danger.
他不顾危险。
相关例句：
He had shown himself careless of personal safety where the life of his colleagues might be at risk
当同事身处危险时他表现英勇，不顾个人安危。
He's always careless and unreliable.
他做事一向马虎，不把牢。
I was careless and stepped in the mud.
不小心一脚踩到烂泥里了。
You are always so careless.
你做事总这么毛糙。
Jenny was careless to let out the secret.
珍妮不小心泄露了秘密。
With a careless flip of his wrists, he sent the ball quickly on its way.
他手腕轻轻一抖，球就飞出去了。