back.牛津词典

at the back of one's mind

• in one's thoughts, but without being of immediate or central concern 在内心中（但并非急事或要事）
• At the back of his mind was the vague idea that he had met her before. 他隐隐约约地觉得以前曾经见过她。

the back of beyond

• an isolated place far from a centre of social and cultural activity 与外界隔绝的地方; 远离闹市的地方
• They live somewhere at the back of beyond. 他们住的地方远离闹市。

back to back

• with back against back 背靠背
• Stand back to back and let's see who's taller. 背靠背站好, 看看谁的个子高。

back to front

• with the back placed where the front should be 前后颠倒
• Your pullover is on back to front. 你的套头毛衣前后穿反了。

be glad, etc to see the back of sb/sth

• be pleased, etc that one will not see sb/sth again 因不再见到某人/物而高兴

behind sb's back 参见to sb's face.

• without sb's knowledge or consent 不让某人知道或不经某人同意; 背着某人
• They say nasty things about him behind his back. 他们在背后说他的坏话。

be on sb's back

• annoy, hinder or persecute sb 惹恼某人; 妨碍某人; 找某人麻烦

break one's `back (to do sth)

• work very hard (to achieve sth) 拚命工作（以实现某目的）

break the back of sth

• finish the larger or more difficult part of (a task) 完成（某项任务的）大部分或较艰难的部分

get/put sb's back up

• make sb angry 使某人生气
• His offhand manner put my back up. 他那随随便便的样子我看着很生气。

get off sb's back

• stop annoying, hindering or persecuting sb 不再惹恼某人; 不再妨碍某人; 不再找某人麻烦

have eyes in the back of one's head

• observe everything (without seeming to do so) 脑袋后边长着眼睛; 留意到一切而不露声色

have one's back to the wall

• be in a difficult position and forced to defend oneself 陷于必须背水一战的困境

know sth like the back of one's hand

• know it very well

make a rod for one's own back

• do sth likely to cause oneself difficulties later 自讨苦吃; 自找麻烦

a pat on the back

• praise for something that you have done well

put one's back into sth

• work at sth with all one's energy 不遗余力地从事某工作; 全力以赴

a stab in the back

• treacherous attack, eg on sb's reputation or position; betrayal 背后的中伤; 背叛行为

stab sb in the back

• attack sb's position, reputation, etc treacherously; betray sb 背地里中伤某人; 背叛某人

turn one's back on sb/sth

• avoid or reject sb/sth 避开或拒绝接受某人/物
• He turned his back on his family when he became famous. 他成名以后对自己家里的人连理都不理。

water off a duck's back

• if criticism, warnings etc are like water off a duck's back, they have no effect on the person you are saying them to

you scratch my back and I'll scratch yours

• used to say that you will help someone if they agree to help you