slip-knot

slip-knot
n
1 knot that can slip easily along the rope on which it is tied, to tighten or loosen the loop 滑结（可沿绳滑动改变松紧者）.
2 knot that can be undone by pulling one end of a rope 活结（拉绳的一端可解开者）.

牛津英汉双解词典