Eyeball hang time is a buzzword that refers to how long a visitor spends on a specific Web page or website. Eyeball hang time can be seen either as a measure of visitor loyalty or the attraction of certain content. The idea is that the stickier the content, the longer viewers will spend looking at it.
Techopedia explains Eyeball Hang Time
Eyeball hang time was one of the many terms to come out of the Internet bubble. Collectively, these terms were known as e-speak or e-lingo. After the Internet bubble burst, many of these terms fell out of use. That said, eyeball hang time is still used occasionally in a marketing context, as in “we need to increase the eyeball hang time on this page” or “the eyeball hang time on the home page is dropping.”