Bounce rate is the percentage of single-page visits or visits in which the person left your site from the entrance (landing) page. Use this metric to measure visit quality - a high bounce rate generally indicates that site entrance pages aren't relevant to your visitors. 

The more compelling your landing pages, the more visitors will stay on your site and  convert. You can minimize bounce rates by tailoring landing pages to each keyword  and ad that you run. Landing pages should provide the information and services  that were promised in the ad copy.