To make a solemn and unbreakable oath or pledge, often by symbolic actions like biting one's arm, signifying extreme resolve and commitment to an alliance or pact.
为了完成这项艰难的任务，他们几人啮臂为盟，誓要一同努力，绝不退缩。
To accomplish this challenging task, the few of them bit their arms and swore an oath, vowing to work together and never back down.
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