The noun 绳索 (shéngsuo) means 'rope' or 'cord.' It is a slightly more formal synonym of 绳子 and is composed of 绳 (rope) and 索 (cord/cable). It is often used in written language and in contexts involving climbing, tying, or securing items.
登山的时候一定要带好绳索。
Dēngshān de shíhou yídìng yào dài hǎo shéngsuǒ.
When climbing a mountain, you must bring rope.
他用绳索把箱子牢牢地绑在车上。
Tā yòng shéngsuǒ bǎ xiāngzi láoláo de bǎng zài chē shàng.
He used a rope to tie the box securely to the car.
救援队靠一根绳索把被困的人拉了上来。
Jiùyuán duì kào yì gēn shéngsuǒ bǎ bèi kùn de rén lā le shànglái.
The rescue team pulled the trapped person up with a rope.