informal to put a lot of effort into doing something.
I'm not going to break my back working for £120 a week!
(often + doing something)
break (one's) back
To put forth a great deal of effort. I've been breaking my back trying to get a passing grade this semester, so failing by two measly points is incredibly frustrating.Don't break your back trying to please these people—they'll never appreciate it.
break one's back
(to do something) Go to break one's neck (to do something).
break your ˈback doing something/to do something
work very hard to achieve something: I’ve been breaking my back to sell as many books as I can. ▶ ˈback-breaking adj. (of physical work) very hard and tiring