1. a second burst of energy, an additional boost
I was tired, but I got a second wind and kept going
A 'second wind' is a noun used to describe a renewed energy or drive to continue something difficult. In sport, a 'second wind' is also known as 'runners high' and refers to the ability of someone to breathe easily after being out of breath or a rush of energy. "I was feeling tired and just about to give up on this when I got a second wind and now I'm almost finished." This is more likely to be heard in a social context.