informal to be careful of the people around you, making sure that they do nothing to harm you.
It's a rough neighbourhood so watch your back when you're walking around the streets.
(redirected from watch back)
watch (someone's) back
To be willing and prepared to help or defend someone; to look out for someone in case they need assistance. Don't worry about those thugs, buddy. I'll watch your back if they ever come bother you again.You can always rely on your parents to watch your back.
watch your (or someone's) back
protect yourself (or someone else) against danger from an unexpected quarter.