The rate of visitors that enter your website and choose to leave after viewing only one page, and ‘bounce’ away. A high bounce rate will negatively impact your SEO. The percentage of users entering your website and leave without engaging with your content or visiting other pages on your website. Depending on the functionality and design of your website this may or may not be cause for concern. A high bounce rate on a 1 page designed website is fairly usual.

Other factors which may cause a high bounce rate –

Poorly designed / poorly laid out navigation
Slow loading website
Too many advertisements / relevant content to what the user expected.
Click – Each unique click through that channel