na-adjective, noun
Describes acting without thinking, often impulsively or carelessly. Can be used as a noun or adjectival noun (〜な).
彼の無考えな発言がみんなを怒らせた。
His thoughtless remark made everyone angry.
無考えに行動すると、あとで後悔するよ。
If you act rashly, you'll regret it later.