not caring about the possible effects of your words or actions on other people 粗心大意的；欠考虑的；轻率的 a thoughtless remark 欠考虑的话
Extra ExamplesIt was thoughtless of him to take the car without checking first. 他不先检查一下就买下那辆车，真是太轻率了。 It was thoughtless to spring it on you so suddenly. 如此突然地将它洒在你身上是没有思想的。 There could be a serious accident as a result of their thoughtless actions. 他们若有所思的举动可能会导致严重的事故。