expression, godan verb (-ru)
train in military arts
Rare, literary expression for practicing martial or military skills. In modern Japanese, 武術を磨く or 武道を稽古する are more common.
古の武士は日々武を練った。
Warriors of old trained in military arts daily.
The phrase combines 武 (bu, 'military arts') with 練る (neru, 'to knead, polish, train'). The exact historical origin is uncertain, but it follows a classical pattern of using 練る for refining skills.