na-adjective, noun
fierce; daring; savage; intrepid
Describes a person or action that is bold, aggressive, and unyielding, often with a nuance of wildness or ferocity. Literary and somewhat old-fashioned; not common in everyday speech.
彼の剽悍な戦いぶりに敵は圧倒された。
His fierce fighting overwhelmed the enemy.
剽悍な気性の持ち主で、誰にも止められなかった。
He had a savage temperament and could not be stopped by anyone.
The word is composed of 剽 (ひょう, 'swift' or 'agile') and 悍 (かん, 'fierce' or 'wild'). The exact historical derivation is uncertain, but the combination suggests a swift and fierce nature.