By the seat of one's pants
在没有事先准备或计划的情况下，凭直觉或临时发挥完成某事。
用于描述临时抱佛脚或即兴发挥的场景。
例句
She passed the exam by the seat of her pants, having studied only the night before.
典故来源
源自早期航空术语，飞行员靠身体感受飞机震动来判断飞行状态，而非仪表。