What does high bounce rate generally indicates?

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

Bounce rate is an inherently subjective measure of performance. That is, you shouldn't really compare your bounce rate to that of other websites other than for entertainment purposes.