Explanation: When a boxer was getting beaten so badly, the coach or manager would throw a towel in to stop the fight. This phrase can be used outside of boxing to simply express quitting.
I was ready to throw in the towel, but I stayed with it.
He's not a quitter, so he's not going to throw in the towel.
I saw a fight last almost two hours before one guy threw in the towel.
A:
The boxing match is great.
B:
One guy is really getting beat up.
A:
Do you think he's going to give up?
B:
He's not going to throw in the towel, they rarely do that these days.
Other Common Sentences
There's no chance for me to win. I'm calling it quits.
I don't think I can win, so I'm going to give up.
I'd rather surrender than get the hell beaten out of me.