Reckless or rash; acting without due thought, often ill-advised or dangerous.
無謀な運転は自分も他人も危険にさらす。
Reckless driving puts both yourself and others in danger.
そんな無謀な計画では成功は難しいだろう。
With such a reckless plan, success will probably be difficult.
無謀さが若さの過ちを生むこともある。
Recklessness can sometimes produce youthful mistakes.