They thoughtlessly planned a picnic without him.

他们考虑不周，安排了一次野餐却没带上他。

《柯林斯英汉双解大词典》

Politicians thoughtlessly promoted home-ownership for those who could not afford it.

政客不加思索地鼓励买不起房的人推广房产。

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As she was crossing to the day-nursery he added thoughtlessly, "And shut that window."

当她走到孩子们的日间活动室去的时候，他又不假思索地加了一句：“把窗子关上。”

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"The decision to postpone the game was taken thoughtlessly and too late, " said Marseille chairman Jean-Claude Dassier.

BBC: Postponement angers French clubs

Credit Bucksbaum's reputation for not jumping thoughtlessly into merger deals at every turn.

FORBES: General Growth Revives The All-Debt Deal

But instead of making that violence profound and impactful, they give us myriad hordes of badguys to thoughtlessly, remorselessly slaughter.

FORBES: [Spoilers follow.]