To be extremely terrified or scared stiff, to the point of losing control of one's bowels and bladder due to intense fright.
看到突然从黑暗中窜出的黑影，他吓得屎屁直流，动弹不得
Seeing the dark figure suddenly dart out from the darkness, he was so terrified that he lost control of his bodily functions and couldn't move.
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