A posture or attitude of preparedness; a stance (physical or mental) taken in readiness or caution.
試合前に選手たちは集中して身構えを取った。
Before the match, the players concentrated and took their stances.
彼は敵の反撃に備えて身構えを崩さなかった。
He kept his guard and did not drop his posture in case of a counterattack.
先生が来ると、生徒は自然と身構えをする。
When the teacher comes in, the students naturally adopt a ready/attentive posture.