look up any word, like timebomb:
 
2.
when your friend, pal, colleague, cheerleader, or someone of a close affinity is by your side (either figuratively or literally) to makes sure that you make it through the troublesome, difficult, or tedious time or predicament you are currently in.
craig: oh, arianna, are you ok?
arianna: i just can't get this cheer down. I don't think I'll be able to do the perfect cheer.

craig: You can do it! I know you can! I got your back.
by arianna-opc August 14, 2011
 
1.
1) An expression assuring someone that you are watching out for them. Comes from making sure you are safe by watching what's behind you when you're busy looking ahead.

2) Can be converted to a threat: "Watch your back," from the possibility someone might injure or kill them from behind when they aren't lookin.
Iono about dis...

Don't trip, Son. I GOT YOUR BACK.
by Joshiro007 February 18, 2003
 
3.
This originally came from old movies and TV shows where two people are in a dangerous situation (usually hunting criminals or other enemies), and one of them is going to venture forward. The other person stays behind and watches for any danger coming from behind or other directions that the first person is unlikely to see. The one who stays behind typically has a weapon, to fend off any attackers.
person 1: "I'm going to look behind that garage."

person 2: "Alright, I've got your back."
by gorkin July 01, 2014