tie the knot 结婚 = to get married
knot （绳等的）结。如to tie a knot打个结。或者换个表达tie in or with a knot打个结。
【翻译】
So when are you two going to tie the knot?
那么你俩什么时候结婚呢？
He caught the rope and knotted it around a post.
他抓住绳子，把它系在一根杆子上。
【翻译】
So when are you two going to tie the knot?
那么你俩什么时候结婚呢？
He caught the rope and knotted it around a post.
他抓住绳子，把它系在一根杆子上。
