环回的英文：
loop back
n. 环，圈；回路；弯曲部分；翻筋斗
v. 打环；以环连结；（使）翻筋斗
The airman looped the loop eight times.
那位飞行员作了八次翻筋斗的飞行表演。
The plane looped the loop three times.
飞机连翻了三个跟头。
Loop the tree with a rope = loop a rope around the tree
将绳子卷绕于树
Loop the curtains up.
把窗帘卷起来。
They looped the thing together.
他们用环将那些东西系在一起。
n. 后面，背面，反面；背，背部；靠背；后卫
v. 支持；后退，倒退；背书；下赌注于
adj. 背部的；后面的；过去的；拖欠的.
adv. 以前；向后地；来回地；上溯
Stand back to back!
背靠背站好！
They are on the back of the menu.
它们在菜单背面。
Our seats on the train were back to back.
我们在火车上的坐位是背靠背的。
It happened far back in the past.
这事发生在久远的过去。
the back of a Chinese robe or jacket
后襟