This is the 13937th most frequent Russian word.
обрежется
"Обрежется" means "will cut oneself" or "will be cut off" depending on context.
In this sentence, 'обрежется' implies that the rope will be cut or severed due to tension.
Если верёвка слишком натянута, она обрежется.
If the rope is too taut, it will cut off.
Here, 'обрежется' denotes an action where an object, the thread, is cut through an external force.
Нитка обрежется, если ножницы острые.
The thread will be snipped if the scissors are sharp.
In this context, 'обрежется' signifies cutting off a portion to enhance or fix an object.